Conference Science and Technology

Munich on QuantumConference Science and Technology

Deutsches Museum, 8/9 July 2019

General Welcome... Information Welcoming Message

... to the first Munich Conference on Quantum Science and Technol- Tuesday afternoon is reserved for two special sessions. First, the ogy at the Center for New Technologies in the Deutsches Museum! topic of gender and physics is addressed. It is important for us to It is organized in the framework of the Cluster of Excellence “Mu- reach many of you with this topic, since one of the main structural nich Center for Quantum Science and Technology” (MCQST, EXC goals of MCQST is to increase the proportion of female scientists 2111) funded by the German Research Foundation (DFG, Deutsche on all levels. Second, we are getting in dialog with industry on Forschungsgemeinschaft). The event marks the starting point of an strategies in quantum science and technology. In a panel discus- annual conference series and brings together quantum scientists sion with attocube, Google, Huawei, Microsoft, and NVision we are from Munich. addressing their plans, visions, and expectations. With 22 invited speakers from Munich and abroad, the talks at the We hope that we have put together an interesting and diverse conference cover all Research Units (RUs) present in MCQST: RU-A: program for you, and that you will enjoy the conference! We are Quantum Information Theory, RU-B: Quantum Simulation, RU-C: looking forward to many exciting presentations and interesting Quantum Computing, RU-D: Quantum Communication, RU-E: discussions, which will create new links between scientists from the Quantum Metrology and Sensing, RU-F: Quantum Matter, RU-G: Munich QST community! Explorative Research Directions. A total of 55 contributed posters by local scientists with a wide variety of topics are an expression of the rich research environment in Munich. With kind regards from On Monday night, we invite you to get together at the Quantum Tatjana Wilk and the MCQST Office Team Science Slam that Microsoft is hosting for us in their Atrium in Schwabing. We have recruited four local quantum scientists for the event. They will talk about their research in an entertaining way, and in the end, the audience’s applause will determine a favorite.

3 General Information Content

Content Information...... 4 Talks...... 6 RU: F - Quantum Matter...... 8 RU: B - Quantum Simulation...... 11 RU: C - Quantum Computing...... 14 RU: A - Quantum Information Theory...... 17 RU: E - Quantum Metrology and Sensing...... 21 RU: G - Explorative Research...... 24 RU: D - Quantum Communication...... 29 Science Slam...... 20 Panel Discussion...... 28 Poster Session A...... 32 Poster Session B...... 46 List of Participants ...... 60 Schedule (Back Cover)...... 64

Organizer Munich Center for Quantum Science und -Technology (MCQST) Schellingstraße 4 D-80799 Munich, Germany www.mcqst.de e-mail: [email protected]

Venue Deutsches Museum Museumsinsel 1 80538 München

Program Committee Prof. Immanuel Bloch (Ludwig-Maximilians-Universität München & Max-Planck-Institut für Quantenoptik) Prof. Ignacio Cirac (Max-Planck-Institut für Quantenoptik) Prof. Jonathan Finley (Technische Universität München) Prof. Rudolf Gross (Technische Universität München & Walther-Meißner-Institut Garching) Prof. Ulrich Schollwöck (Ludwig-Maximilians-Universität München) Prof. Simone Warzel (Technische Universität München) Prof. Harald Weinfurter (Ludwig-Maximilians-Universität München)

Acknowledgment Cover-Photo by Maximilian Kühn, Ligsalzstraße 35, 80339 München, [email protected]

4 General Map Information

Map of the Museumsinsel

Bus Departure for Science Slam

Museum Entrance

Conference in Section ZNT

Deutsches Museum Museumsinsel 1 Telefon: (089) 2179 1 D-80538 München Telefax: (089) 2179 324

www.deutsches-museum.de

Emergency Calls Fire Department & Ambulance: 112 In other cases of urgency you may call the conference Police: 110 organizer on mobile phone: +49 176 78266509

Disclaimer The organizers do not hold any liabilities on damages, losses, health issues, etc.. All participants are advised to take care about their travel and health insurances related to this conference.

5 Invited Talks

Talks

Research Unit A - Quantum Information Theory Research Unit B - Quantum Simulation Research Unit C - Quantum Computing Research Unit D - Quantum Communication Research Unit E - Quantum Metrology and Sensing Research Unit F - Quantum Matter Research Unit G - Explorative Research

6 Invited Overview Talks TBA Boris Altshuler ��8

Atomistic defect states as quantum emitters in monolayer MoS2 Alexander W. Holleitner ��9

Charge density wave quantum criticality in two dimensional metals Matthias Punk ��10

Magnetism and frustration in quantum gases Dan M. Stamper-Kurn ��11

New routes to probe the two-dimensional Fermi-Hubbard model Michael Knap ��12

Synthetic gauge fields with ultracold atoms in periodically-driven lattices Monika Aidelsburger ��13

Quantum computation and quantum simulation with strings of trapped Ca+ ions Rainer Blatt ��14

Quantum microwaves: Secure communication, cryogenic LAN cables, and illumination Frank Deppe ��15

Neural-network approach to dissipative quantum many-body dynamics Michael J. Hartmann ��16

TBA Stephanie Wehner ��17

Quantum advantage with noisy shallow circuits in 3D Robert König ��18

From quantum mechanics to probability theory - and back? Sabine Jansen ��19

Quantum sensing enabled by diamond Fedor Jelezko ��21

Quantum sensors for microwave radiation Friedemann Reinhard ��22

Challenging QED with atomic hydrogen Thomas Udem ��23

New insights into quantum information from black holes Johanna Erdmenger ��24

Analog Quantum Chemistry Simulation with Cold Atoms Alejandro González-Tudela ��25

Using tensor network states for lattice gauge theories Mari Carmen Bañuls ��26

What does gender have to do with physics? Thomas Brage ��27

Quantum Communications in Space: new opportunities for basic science and applications Paolo Villoresi ��29

Towards quantum networks with Erbium dopants Andreas Reiserer ��30

Qubit memories for quantum networks Olivier Morin ��31

7 8 Talks Invited Mon, 9:00 Physics Department, Columbia University, New York, NY 10027, USA Boris Altshuler notes TBA Quantum Matter notes esrmns Te ie hp rvas a reveals shape line dependent The measurements. temperature and troscopy spec- excitation photoluminescence ing perform- by emitters single investigate spectroscopically We [3,4]. quality tical op- their enhance greatly to hBN within 2 ad naslt te eetv MoS defective the encapsulate and [2] luminescence defect active optically ate W Atomistic defectstates asquantumemitters inmonolayerMoS ae MoS layer mono- bombard We [1]. heterostructure ters in a monolayer MoS monolayer a in ters Walter Schottky InstitutandPhysicsDepartment, Technische Universität München, Am Coulombwall 4, 85748Garching, Germany Alexander W.Holleitner Quantum Matter eeain f ige eet emit- defect single of generation deterministic the demonstrate e 2 notes gener to ions helium with 2 van der Waals der van 2 -

few nanometers. Our work paves the way the paves a work nanometers.Our few of precision a with emitters quantum positioning allows methodology strated mi- tunneling demon- The [5]. scanning measurements croscopy of light the in origin their discuss and bombardment ion helium the by induced defects istic atom- to emission the attributeWe nm. 2 of scale length a to localized spatially are emitters the that find our we lines, to emission model Boson independent the Employing phonons. LA/TA with action inter the resembling asymmetry strong 2 -

[5] J. Klein et al., arxiv 1905.01242 (2019). (2019). [4] B. Milleretal. Nature Comm. 10, 807 12383 (2017). [3] J. Wierzbowski etal., Sci. Rep. 7, [2] J. Kleinetal., 2DMater. 5, 1(2017). [1] J. Kleinetal., Nature Comm. (2019). collaboration. fruitful very a for FinleyJ. J. and Schmidt, R. Knap, Watanabe, M. Kaniber, M. K. Wurstbauer, U. Taniguchi, T. Müller, K. Cerne, J. Mitterreiter, E. P. Zimmermann, Barthelmi, K. Hötger, A. Wierzbowski, J. Puentes, S. Sigl, L. Sigger, F. Florian, M. I thank my collaborators J. Klein, M. Lorke, structures. hetero- Waals der van TMDC monolayer in emitters quantum single of generation deterministic and controlled the towards References Invited Talks Mon, 9:45 9 10 Talks Invited Mon, 10:10 W Fakultät fürPhysik, LMUMünchen, Germany Johannes Halbinger, DimitriPimenov, Matthias Punk Charge densitywavequantum criticalityintwodimensionalmetals hs tastos n ter theoretical their and transitions phase quantum of vicinity the in found areoften liquids non-Fermi Such framework. liquid Fermi the into fit not do which phases lic metal- strange exhibit materials electron correlated strongly various theory, liquid notes Fermi Landau’s within described well very are metals ordinary hile f aeil sc a tasto mtl di- metal transition as such materials of [1], which have been observed in a variety metals two-dimensional quasi in points critical quantum wave density charge of example specific the discuss prob- will we the lem to introduction short a After physics. matter condensed in problem open challenging a remains description Quantum Matter References iuu tasto i saiie b a dy- theFerminamical nestingof surface. a by stabilized is transition tinuous con- the that show and approach group critical renormalization controlled a quantum using point the characterize We tellurides. rare-earth and chalcogenides Phys. Rev. B99, 195102(2019). [1] J. Halbinger, D. Pimenov, andM. Punk, notes n oi-tt mtras bt nw i an in now, but, materials, solid-state in typically appear that phenomena study to us allow systems These ex known. actly is systems construction microscopic quantum whose many-body create U Magnetism andfrustration inquantumgases Quantum Simulation Department of Physics, California,Department of Universityof Berkeley, CA 94720, USA Dan M. Stamper-Kurn notes to us allow physics atomic of ods meth- the and gases atomic ltracold - the construction of lattices characterized lattices of construction the gas, quantum a in condensation magnon of realization the frustration: geometric and magnetism of studies toward gases atomic ultracold of applications three ent precisely pres- will I is controlled. and characterized that setting experimental metal elements. transition- of gases ultracold produce to frustration,geometric effortby new a and Invited Talks Mon, 11:00 11 12 Talks Invited Mon, 11:45 matrix product state based algorithms to algorithms based state product matrix particular,develop provide.In we scopes micro- gas quantum perspective new the by motivated results recent present we experi- decades.Here,past the in studies mental and theoretical of amount vast a of subject the been have conductivity super high-temperature to connection T PhysicsandInstitutefor DepartmentAdvanced Study, of Technical Munich, Universityof Germany A. Bohrdt, F. Grusdt, C. S. Chiu, G. Ji. M. Xu, D. Greif, M. Greiner, E. Demler, andMichaelKnap New routes toprobe thetwo-dimensionalFermi-Hubbard model notes its and model Fermi-Hubbard sional two-dimen- the of diagram phase he - relations in the finite temperature and fi- and temperature finite the in relations cor spin for picture effective simple this compare furthermore We chargons. and anti-ferromagnetic spinons of state bound a an as environment in moving hole doped a by captured well be can namics dy- effective The [1]. temperatures and high low at both scales relevant the tify anti-ferromagnetic background and iden- the in hole single a of dynamics the study Quantum Simulation - References on themicroscopic level[3]. best system the describes theory which determine to order in categories oretical the- different into doping finite atdata tal experimen- classify to approach learning machine a develop we experiment, and theories of comparison unbiased an For [2]. agreement remarkable find and ment nite doping regime of a cold atom experi- (2018); acceptedinNature Physics [3] A. Bohrdt, etal. ArXiv:1811.12425 (2018); acceptedinScience [2] C. Chiu, etal. ArXiv:1810.03584 [1] A. Bohrdt, F. Grusdt, MK (2019) notes system. This method facilitated the direct the facilitated method Thissystem. static non-trivial a of properties the late emu- to parameters systems’ the of lation modu- periodic on relies It [2]. gineering topological band structures is Floquet en- generating for technique widespread A the quantumHalleffect. is examples prominent most the of One properties. conductivity unique exhibit matter of states Topological [1]. models lattice topological paradigmatic of tion realiza- successful the after emerged tion direc- new promising Recently,a physics. statistical to condensed-matter from ranging phenomena of variety a study to U Synthetic gaugefieldswithultracold atoms inperiodically-drivenlattices Quantum Simulation Max-Planck-Institut fürQuantenoptik, Hans-Kopfermann-Strasse 1, 85748Garching, Germany Fakultät fürPhysik, Ludwig-Maximilians-Universität München, 80799Munich, Germany Monika Aidelsburger notes platforms experimental powerful are lattices optical in atoms ltracold f nmlu cia eg mds For modes. edge chiral anomalous of appearance the to leads which number, spectrum can exhibit a non-trivial winding quasienergy The [4]. counterparts static their of those beyond well go however, systems, Floquet of properties rich The ry coupledtomatter [3]. minimal model of a Z2 lattice gauge theo- a implemented and developed have we matter and gauge fields. Inspired by these ideas, between interaction an require which theories, gauge complete even or fields gauge density-dependent gineer niques have further been proposed to en- tech- Floquet fields. gauge synthetic with lattices optical in currents chiral and ties proper topological bulk of observation - References and edge-state properties thesystem. of bulk the of measurements direct through potential to reveal these intriguing phases the have atoms Cold modes. edge chiral protected topologically by characterized is bands bulk trivial topologically with tor insula- Floquet anomalous an instance, 235114 (2010). [4] T. Kitagawaetal., Phys. Rev. B82, (2019). [3] C. Schweizeretal., arXiv:1901.07103 (2017). [2] A. Eckardt, Phys. Mod. Phys. 89, 311 91, 015005(2019). [1] N. R. Cooper etal., Phys. Mod. Phys. Invited Talks Mon, 12:10 13 Invited Talks Quantum Computing Mon, 14:30 Quantum computation and quantum simulation with strings of trapped Ca+ ions

Rainer Blatt Institute for Experimental Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Otto-Hittmair-Platz 1, A-6020 Innsbruck, Austria

he state-of-the-art of the Innsbruck ion string are investigated [2] and used creation [3] and using a hybrid-classical Ttrapped-ion quantum computer is for quantum simulations. ansatz, we determine steady-state prop- briefly reviewed. We present an overview erties of the Hamiltonian. Hybrid classical- on the available quantum toolbox and In the second part, we present both the quantum algorithms aim at solving opti- discuss the scalability of the approach. digital quantum simulation and a hybrid mization problems variationally, using a Fidelities of quantum gate operations quantum- classical simulation of the Lat- feedback loop between a classical com- are evaluated and optimized by means tice Schwinger model, a gauge theory of puter and a quantum co-processor, while of cycle-benchmarking [1] and we show 1D quantum electrodynamics. Employ- benefitting from quantum resources [4]. the generation of a 16-qubit GHZ state. ing universal quantum computations, Entangled states of a fully controlled 20- we investigate the dynamics of the pair-

References

[1] A. Erhard et al., arXiv:1902.08543 (2019).

[2] N. Friis et al., Phys Rev X. 8 021012 (2018).

[3] E. A. Martinez et al., Nature 534, 516 (2016).

[4] C. Kokail et al., Nature 569, 355–360 (2019).

14 notes notes Invited Quantum Computing Talks Mon, 15:15 Quantum microwaves: Secure communication, cryogenic LAN cables, and illumination

Frank Deppe1,2,3 1Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany 2Physik-Department, Technische Universität München, 85748 Garching, Germany 3Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 München, Germany

he research on quantum microwaves to one-time pad cryptography will be We acknowledge support by the Ger- Temitted from superconducting cir- discussed [1]. In the outlook, ideas on dis- many’s Excellence Strategy EXC-2111- cuits has advanced from the realm of tributed quantum computation, quantum 390814868, Elite Network of Bavaria pure basic research to the demonstra- microwave communication, and quantum through the program ExQM, the Europe- tion of first protocols employing nonclas- radar targeted within the European Flag- an Union via the Quantum Flagship proj- sical correlations. After a brief recap of ship project “Quantum Microwaves for ect QMiCS (Grant No. 820505). the WMI activities in this field, a recent Communication and Sensing (QMiCS)” result on the nonlocal preparation of a [2] are presented. squeezed state and its intricate relation

References

[1] S. Pogorzalek et al., Secure quantum remote state preparation of squeezed microwave states, Nat. Commun. 10, 2604 (2019).

[2] https://qmics.wmi.badw.de/

15 notes 16 Talks Invited Mon, 15:40 ial i te om f aitoa Monte Carlo approaches variationaland quantum mechani- of form the in clas- sically role, significant a play algorithms variational scenarios, both In computers. quantum of applications first interesting for candidate good a thus are and puters 1 Q 4 3 2 Michael J.Hartmann Neural-network approach todissipative quantummany-bodydynamics Center forComputational QuantumPhysics, Flatiron Institute, 1625th Avenue, New York, NY 10010, USA PhotonicsandQuantumSciences, Instituteof Heriot-Watt UniversityEdinburgh EH144AS, UnitedKingdom GoogleResearch, Erika-Mann-Str. 33, 80636München, Germany Physics, Erlangen-Nürnberg Department (FAU), of Universityof 91058Erlangen, Germany notes are com- classical with simulate to hard systems many-body uantum notes 1,2,3 andG. Carleo 4 their coupling to an environment into ac- into environment an to coupling their take and isolated perfectly not systems are that quantum of situation relevant experimentally the on focus will I ticular par In [1]. techniques learning machine on based is that algorithm variational cal classi- a introduce will I talk this In rithms. cally in the form of variational hybrid algo- Quantum Computing - References for adissipative spinlattice system. examples approachnumerical the with of accuracy the illustrate I technique. Carlo Monte- variational a using evolution time its integrates and machines Boltzmann restricted of form the in networks neural with states quantum many-body mixed count. Therepresentsthus algorithms the Rev. Lett., inprint, arXiv:1902.05131. [1] M. J. Hartmann andG. Carleo, Phys. notes Quantum InformationTheory notes QuTech, Delft Universityof Technology, Delft, Netherlands Stephanie Wehner TBA Invited Talks Mon, 16:30 17 Invited Talks Quantum Information Theory Mon, 17:15 Quantum advantage with noisy shallow circuits in 3D

Sergey Bravyi, David Gosset, Robert König and Marco Tomamichel IBM Watson University of Waterloo, Canada TU München, Germany University of Technology Sydney, Australia

rior work has shown that there exists a The corresponding quantum algorithm is value. On the other hand, the problem Prelation problem which can be solved the simplest we know of which achieves cannot be solved with high probability by with certainty by a constant-depth quan- a quantum advantage of this type. It may a noise-free classical circuit of constant tum circuit composed of geometrically also be more practical for future imple- depth. A key component of the proof is a local gates in two dimensions, but cannot mentations. Our second, main result, is quantum error-correcting code which ad- be solved with high probability by any that a separation persists even if the shal- mits constant-depth logical Clifford gates classical constant depth circuit composed low quantum circuit is corrupted by noise. and single-shot logical state preparation. of bounded fan-in gates. Here we provide We construct a relation problem which We show that the surface code meets two extensions of this result. Firstly, we can be solved with near certainty using these criteria. To this end, we provide show that a separation in computational a noisy constant-depth quantum circuit a protocol for single-shot logical state power persists even when the constant- composed of geometrically local gates preparation in the surface code which depth quantum circuit is restricted to geo- in three dimensions, provided the noise may be of independent interest. metrically local gates in one dimension. rate is below a certain constant threshold

18 notes notes Invited Quantum Information Theory Talks Mon, 17:40 From quantum mechanics to probability theory - and back?

Sabine Jansen LMU München, Mathematisches Institut, Theresienstr. 39, 80333 München, Germany

any-body systems - quantum, but by investigating operators (Stein opera- ics. Conversely, probability theory some- Malso classical - are challenging. tors, infinitesimal generators) and their times helps address problems in quantum Many methods originated in quantum spectral gap; duality of Markov process- statistical mechanics, e.g. via path inte- mechanics prove helpful in understand- es, a notion related to unitary equivalence grals. The talk highlights some of those ing classical systems: Metastability and of Hamilton operators and different rep- possible points of contacts between and the rigorous proof of Arrhenius laws build resentations for algebras of creation and probablity theory and quantum theory. on the semi-classical limit and WKB ex- annihilation operators, is tremendously pansions; spatial correlations are studied helpful in mathematical population genet-

References

[1] S. Jansen, E. H. Lieb, R. Seiler: Symmetry breaking in Laughlin’s state on a cylinder Commun. Math. Phys. 285, 503-535 (2009).

[2] S. Jansen, P. Jung: Wigner crystallization for the quantum 1D jellium at all densities Commun. Math. Phys. 331, 1133-1154 (2014).

[3] S. Jansen, N. Kurt: On the notion(s) of duality of Markov processes Probab. Surveys 11, 59-120 (2014).

19 notes 20 Information General Mon, 19:30-21:30 MCQST is all about quantum science and technology, the talks will focus primarily on quantum related themes. With this event, this With MCQSTthemes. aimstobringquantumscienceintofocusinanunderstandableandengagingway. related quantum on primarily Since focus favourite.will talks a the technology, determine and science and quantum presentations about all the is MCQST evaluate will applause audience’s the end, the entertaining an In way.in 10-minutes comprehensive in researchand state-of-the-art and issues complex present scientists which in talks of series a of sists con- slam science Germany. Microsoft A with collaboration in organized Slam Science Quantum first its presentsMCQST proudly Talking Quantum–ScienceSlam Host Our QuantumSlammers Matthias Mader|LMUMünchen Nicolas Tolazzi Frauke Seeßelberg |ScienceSlammerAlkaLove Ivana Kurečić QuantumOptics|Policy |MaxPlanckInstituteof Control Theory Markus Hasenöhrl | Defusing abomb-thequantumway TU Munich| Conference in SectionZNT | Max Planck Institute of QuantumOptics|A PhotonLove| MaxPlanckInstituteof Story Bus Departure for ScienceSlam Museum Entrance Walter-Gropius-Str. 5, 80807Munich Microsoft Atrium Destination: Departure viaBusbetween18:15and18:50 Science Slam notes E Quantum sensingenabledbydiamond Quantum Metrology&Sensing resolution. nanometer with sensing and munication com- quantum secure communication, and processing information quantum as such applications, interesting of number a opened approachconditions. new This ambient under readout and control spin single coherent allowing diamond in ters cen- defect of study the were to applied also techniques resonance spin magnetic single recently temperatures, at low molecules aromatic with done were quantum systems. While first experiments single of transitions resonance magnetic detect to possible it making techniques these of combination a is development matter.recent condensed A in molecules single of detection able the demonstrate is to which spectroscopy molecule single optical of to sensitivity excellent contrasted the be may This insensitive. very as also but substance possible every almost informationon detailed very vides Institute of QuantumOptics,Institute of UlmUniversity, Germany Fedor Jelezko notes pro- that technique spectroscopic a is resonance spin nuclear and lectron etoa slto sae M. e tech- New NMR. state solution conventional of that to comparable resolutions spectral reach must magnetometers NV purpose,However,biomolecules.that for single of structure and dynamics raveling un- towards way the open experiments (NMR) resonance magnetic nuclear ecule Single-mol- protein. single a from signal the of detection label-free and markers demonstra - paramagnetic by labeled proteins of principle tion of proof first the enabled diamond of surface the to teins proof attachment and centers NV single of implantation by biomolecules to close few angstroms.sensor a the bring Theto ability within position their resolve and for detecting single external nuclear spins amond currently have sufficient sensitivity di- in centers color (NV) vacancy nitrogen Single spins. nuclear external of ensembles small or spins nuclear individual of nanometer scales, including the detection nucleartection of magnetic resonance on amond based quantum sensing is the de- A particularly interesting application of di- spin state of individualcolorcenters spin state of photoionizationcan provide robust and efficient access to selective spin on base centers NV of detection photoelectrical that shown was it Recently centers. color NV single of detection optical on based are centers diamond with ob- far results so tained above mentioned of Most conventional MRIimaging. of sensitivity of enhancement the for ing promis- very arepolarization spin nuclear dynamic for techniques based diamond NV centers to external nuclear spins. Such of spins polarized optically from ization polar transferthe of enables also centers NV by spins nuclear sense entanglement. to ability The quantum employs that realizedand recently technique including purpose this for proposed were niques Invited Talks Tue, 9:00 - 21 22 Talks Invited Interestingly, virtually all existing sensors existing all virtually Interestingly, detect currents inalivingbrain [2]. drive write heads [1], and atomic vapor cells hard of field magnetic the image to used ments, experi- Nitrogen-Vacancy arebeing centers flagship In technology. of quantum applications real-world for candidate M TU München, Walter Schottky InstitutandPhysik-Department, 85748Garching, Germany T. Joas, A.M. Waeber, D.M. Irber, G. Braunbeck, Friedemann Reinhard Quantum sensorsformicrowave radiation Tue, 9:45 notes front-runner a become have qubits spin on based sensors field agnetic efforts of our group and others to fill it. to andothers group our of efforts the review and white map, sensing the on this spot for reasons the discuss will I to liveinthisrange. happen themselves transitions qubit the that given surprising is which explored, under- remained has signals frequency frequencies GHz- of sensing Quantum MHz). 10 - (DC low at fields targeting are Quantum Metrology&Sensing References ht ol poie estv detectors and amplifiersformicrowave radiation. sensitive provide could that devices cavity-QED room-temperature on based hardware sensing novel as well as [3,4], sensing high-frequency for cols proto- dedicated on work includes This (2018). [5] J.D. Breeze etal., Nature 555, 493 tions 8, 1105(2017). [4] A. Stark etal., Nature Communica- 8, 964(2017). [3] T. Joas etal., Nature Communications ogy 12, 67(2017). [2] I. Jakobi etal., Nature Nanotechnol- Magnetoencephalography, 993(2014). [1] S. Knappe, T. Sander, L. Trahms in notes Invited Quantum Metrology & Sensing Talks Tue, 10:10 Challenging QED with atomic hydrogen

L. Maisenbacher, A. Beyer, V. Andreev, A. Grinin, A. Matveev, K. Khabarova, N. Kolachevsky, R. Pohl, D. Yost, T. Hänsch and Thomas Udem Max-Planck Institute of Quantum Optics, 85748 Garching and Ludwig-Maximilians-Universität München

recise determination of transition fre- to the hydrogen data if QED calculations compatible with the value obtained from Pquencies of simple atomic systems are assumed to be correct [2]. In order to muonic hydrogen with an uncertainty that are required for a number of fundamen- shed light on this discrepancy the transi- is comparable to the previous hydrogen tal applications such as tests of quantum tion frequency of one of the broader lines world data [3]. Meanwhile Hélène Fleu- electrodynamics (QED), the determina- in atomic hydrogen has to be measured rbaey and her team at the Laboratoire tion of fundamental constants and nu- with very good accuracy. For this pur- Kastler Brossel, Paris have re-measured clear charge radii. The sharpest transition pose, we have employed our previous the 1S-3S transition frequency with a sig- in atomic hydrogen occurs between the 1S-2S apparatus as a cold source of la- nificantly improved accuracy and find the metastable 2S state and the 1S ground ser excited 2S atoms in order to perform previous “regular hydrogen charge ra- state with a natural line width of only spectroscopy on the 2S-4P transitions. dius" [4]. At our lab, we have also been 1.3 Hz. Its transition frequency has been With a natural line width of 12.7 MHz, working on this transition with a different measured with almost 15 digits accuracy large Doppler effects, quantum interfer- method. We hope to be ready to report a using an optical frequency comb and a ence etc. a good line shape analysis is result soon. This will provide a unique op- cesium atomic clock as a reference [1]. A mandatory to identify the true transition portunity to compare two highly accurate measurement of the Lamb shift in muonic frequency. Our result on this transition measurements obtained at different labs. hydrogen is in significant contradiction yields a value for the proton radius that is

References

[1] C. G. Parthey et al., Phys. Rev. Lett. 107, 203001 (2011).

[2] A. Antognini et al., Science 339, 417, (2013).

[3] A. Beyer et al., Science 358, 79 (2017).

[4] H. Fleurbaey et al. PRL 12).0, 183001 (2018).

23 notes 24 Talks Invited I Lehrstuhl für Theoretische PhysikIII, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg R. Abt, New insightsintoquantuminformation from blackholes Tue, 11:00 h etnln rgo. n h tl I will I talk the In region. entangling the of boundary the shares that space AdS in surface minimal a of area the to mapped be may theory field a of entropy entanglement the Takayanagi, and Ryu area.by proposedhorizon As its of terms in hole black a of entropy the gives that formula Bekenstein the to analogy ary,in bound- d-dimensional its in encoded is a in stored tion informa- the that states which principle, holographic the on based is duality This gravity. and theory field quantum tween be- relation duality new a provides CFT AdS/ correspondence. theory) field mal space/Confor Sitter (Anti-de the AdS/CFT of generalizations of context the space-times, in hyperbolic in holes black of properties the to theory information ments that relate concepts of quantum of concepts relate that ments will give an overview over new develop- Johanna Erdmenger dmninl conformal d-dimensional notes volume d+1-dimensional d+1-dimensional , M. Gerbershagen, H.Hinrichsen, C.M. Melby-Thompson, R.Meyer, C. Northe, I. A. Reyes - transition betweenbothphasesisobserved. Right: A theblack-hole simulation of geometryusingIsingspinsinwhichthepredicted The RT surfacehastwophases, aconnectedanddisconnectedone. Left: theRyu-Takayanagi Phasetransition of (RT) surfaceforthree-dimensional blackholes: state in the Hilbert space, and on recent on and space, Hilbert the in state reference state in order to reach any other given a to applied be to need that gates quantum of number the i.e. for complexity, results recent on particular in focus Explorative Research References approach. space are reproduced in a tensor network hyperbolic the of topology the involving Results holes. black using complexity of realization dual a providing for proposals (2019) 012[arXiv:1805.10298[hep-th]]. plexity from Kinematic Space, JHEP 1901 Northe, Holographic Subregion Com- shagen, C. M. Melby-Thompson andC. [2] R. Abt, J. Erdmenger, M. Gerber th]]. no.6, 180003[arXiv:1710.01327[hep- in AdS3/CFT2 , Fortsch. Phys. 66(2018) and I. A. Reyes, Topological Complexity M. Melby-Thompson, R. Meyer, C. Northe [1] R. Abt, J. Erdmenger, H. Hinrichsen, C. - notes are focused on finding on efficient algo- efficient on finding on focused efforts are Current technologies. quantum future of applications exciting most the S 5 4 3 2 J. Arguello-Luengo 1 Analog QuantumChemistrySimulation withCold Atoms Explorative Research CASKey Laboratory of Theoretical Physics, Instituteof Theoretical Physics, Sciences, Chinese Academy of Beijing100190, China Max-Planck-Institut fürQuantenoptik, Hans-Kopfermann-Straße 1, D-85748Garching, Germany Center forQuantumPhysics, Innsbruck, Universityof A-6020 Innsbruck, Austria InstitutodeFísica Fundamental IFF-CSIC, Calle Serrano 113b, Madrid28006, Spain ICFO-InstitutdeCienciesFotoniques, The Scienceand Barcelona Institute of Technology, E-08860, Castelldefels (Barcelona), Spain with a quantum computer is one of of one is computer quantum a with problems chemistry quantum olving 1 notes , Alejandro González-Tudela n iuaig unu ceity prob- chemistry quantum simulating in consists which problem the to approach complementary a present will I [1], talk chemistry problems in a digital way. In this of simulation efficient the allow that rithm 2 , TaoShi 3 , P. Zoller 4 , J. I. Cirac 5 it withsimplemolecules. benchmark then and Hamiltonian, the of parts different first the simulate to will how show I atoms. ultra-cold using lems References [1] arXiv:1807.09228. Invited Talks Tue, 11:45 25 26 Talks Invited and sizes of the systems amenable to TN to amenable systems the of sizes and dimensions the While them. for scenario a challenging offer version, Hamiltonian their in Theories, Gauge Lattice systems. body many quantum correlated strongly T Using tensornetworkstates forlattice gaugetheories Tue, 12:10 Max-Planck-Institut fürQuantenoptik, HansKopfermann Str. 1, 85748Garching (Germany) Mari Carmen Bañuls notes techniques for power their (TN) demonstrated have Network ensor dynamics. out-of-equilibrium or potential, chemical a of presence the as such tackle, easily cannot techniques standard more which problems for used readily be can works Net- Tensor simulations, Carlo Monte by achievable those from far still are studies Explorative Research discrete lattice formulation. their through theories field continuum of solution the targeting particular in area, this in work recent the of some present Tensor of will I talk methods.this Network In application particular this in increasing interest an seen have years last The notes Invited Diversity Talks Tue, 14:30 What does gender have to do with physics?

Tomas Brage Division of Mathematical Physics, Department of Physics, Lund University, 221 00 Lund, Sweden

hysics is often seen, by Physicists not cists and I will combine a discussion of meritocracy” could be one key to under- Pthe least, as an objective Science and these with some general theory and per- stand the lack of women in the field. The we believe we are surrounded by a “cul- sonal experiences, to paint a picture on talk is intended as a translation of results ture without culture”. At the same time our how gender transgresses Physics, like all from recent progress in Gender Science history, class- and board rooms are domi- other fields. By using the three levels of to an audience of non-experts in the field, nated by men. This is a clear paradox that change introduced by Schiebinger, I re- especially people within STEM-fields. The should awaken the curiosity of anyone. In fer to studies of e.g. Anthropologists and aim is to give some answers, but also to this talk I will give some examples on how Psychologists. The bias against women, show that this is an extremely interesting you can approach the question in the title. due to the fact that Physics is stereotypi- and active research field. There have been several studies of Physi- cally male, combined with the “myth of

27 notes 28 Information General Host Our guests are how) (and When model: business QSTtheir and goals long-term and short- expectations, and aims companies’ the us about their activities. We will talk about tell to and (QST) technology and science quantum in interest companies’ their us with share to them ask will and industry from guests few a invited ogies.have We C "Challenges inquantumscienceandtechnologiesfrom basicresearch toapplications" Panel Discussion Tue, 15:15 Jonathan Finley |Professor at TU Munich Walter Weigel | Vice-President theHuaweiEuropean of Research Institute Natalie Kilber| Technical Consultant at Microsoft DeutschlandGmbH Khaled Karrai |Co-Founder &ScientificDirector at attocube systems AG Markus Hoffmann |GlobalQuantumComputing Practice Lead at GoogleGermanyGmbH ExecutiveSella Brosh Officer at |Chief NVision Imaging TechnologiesGmbH rently investing in quantum technol- quantum in investing rently cur are world the over all ompanies - and China? USA with compete Europe Can industry? can scientists gain from collaboration with how And scientists? from expect dustry in- does QST.What in goals the towards academia and industry can work together how discuss to like would we Moreover, QST branch? their from profit make to expecting they Panel Discussion ates? gradu- QST future of skills the on tions expecta- have companies Do like? look community this should How community. QST a forming in interested are panies Further, we would like to know the if com- notes Invited Quantum Communication Talks Tue, 16:30 Quantum Communications in Space: new opportunities for basic science and applications

Paolo Villoresi Dipartimento di Ingegneria dell’Informazione, Università degli Studi di Padova, Padova, Italy

uantum Communications are based perposition principle on a Space channel exchange scale has now reached the level Qon degrees of freedom (DoF) of [1,2] and are recently considered for an of 250 ps along a real space channel [5] light that allow for the sharing of quantum Optical Test of the Einstein Equivalence and the altitude of 20000 km [6] respec- states over long distances. The DoF for Principle [3]. tively, as well the Space extension of the Space links are of interest to address the John Wheeler wave-particle gedankenex- interplay of Quantum Physics and Gravity A relevant development in the Lab use of periment [7]. as well as the applications as QKD on very the temporal modes includes the intro- long scales. duction of a scheme free from the post- The QC experiments along Space chan- selection loophole, when entangled stat- nels were realized at MLRO - Matera La- We shall describe some steps forward in ed, that may be extended to free-space ser Ranging Observatory of the ASI Italian the use of temporal modes for free-space channels [4]. Moreover, the experimental Space Agency, in Matera, Italy. Quantum Communications (QC). These efforts to improve both the resolution in were initially used to investigate the su- the temporal detection and the photon

References

[1] G. Vallone, D. Dequal, M. Tomasin, F. Vedovato, M. Schiavon, V. Luceri, G. Bianco, and P. Villoresi, “Interference at the Single Photon Level Along Satellite- Ground Channels,” Phys. Rev. Lett. 116, 253601 (2016).

[2] C. Agnesi, F. Vedovato, M. Schiavon, D. Dequal, L. Calderaro, M. Tomasin, D. G. Marangon, A. Stanco, V. Luceri, G. Bianco, G. Vallone, and P. Villoresi, “Ex- ploring the boundaries of quantum mechanics: advances in satellite quantum communications,” Philos. Trans. R. Soc. A Math. Phys. Eng. Sci. 376, 20170461, (2018).

[3] D. R. Terno, F. Vedovato, M. Schiavon, A. R. H. Smith, P. Magnani, G. Vallone, and P. Villoresi, “Proposal for an Optical Test of the Einstein Equivalence Prin- ciple,” arXiv: 1811.04835 (2018).

[4] F. Vedovato, C. Agnesi, M. Tomasin, M. Avesani, J.-Å. Larsson, G. Vallone, and P. Villoresi, “Postselection-Loophole-Free Bell Violation with Genuine Time-Bin Entanglement,” Phys. Rev. Lett. 121, 190401 (2018).

29 notes 30 Talks Invited u nds eaae b u t 13 km 1.3 to up by separated nodes tum quan- two of entanglement the onstrated While pioneering experiments have dem- surement. mea - precision and communication, tum quan- processing, information quantum distributed in applications numerous and theory quantum of tests fundamental el facilitatenov- quantum-controlledsystem a in available correlations non-local and entanglement the however, classi- devices, to cal contrast In Internet. the form to up wired like are computers conventional just channels, quantum by nected A Quantum Networks Group, QuantumOptics, MPIof Garching, Germany B. Merkel, L. Weiss, A. Gritsch, P. Cova Fariña, Towards quantumnetworks withErbiumdopants Tue, 17:15 notes con- are that processors quantum of consist will network quantum future optically excited states. hampered by the ms-long lifetime their of been has ions erbium individual nessing har However, minimal. is fibers optical in loss where [4] window frequency tions with telecommunica- the in transitions [3] optical coherence ground-state long second- combines system silicate This crystals. into doped ions erbium vidual indi- explores group our context, this In existing physical seemsmandatory. of bottlenecks the overcomes tances. To this end, a new technology that largerdis- and morenodes prototypesto these of scaling requires networks tum quan- of potential full the [1,2],accessing Andreas Reiserer Quantum Communication - References crystals. erbium-doped with networks quantum global realizing towards outlook an give and experiments these of status current [4].presentdopants will erbium the I with we approach, combine siliconnano-photonicstructures second a In resonators. thin silicate crystals into cryogenic Fabry-Perot micrometer embed we approach, experimental first a In volume. mode cal high quality of factor with ultra-small opti- resonators using magnitude of orders al sever by reduction lifetime precedented un- an target We [1]. resonators optical We plan to overcome this challenge using 243601 (2018). [4] A. M. Dibosetal. Phys. Rev. Lett. 120, (2018). [3] M. Rančić etal., Nat. Phys. 14, 50 (2015). [2] B. Hensenetal., Nature 526, 682 Phys. 87, 1379(2015). [1] A. Reiserer andG. Rempe, Rev. Mod. - notes en hw t b poiig platforms. promising be to shown been have electrodynamics quantum cavity on based Systems interaction. efficient light-matter an offering systems from built be to need memories quantum photons, single by transferred and carried are bits qu- where networks, quantum of context the In protocols. information quantum of Q Max-Planck-Institut fürQuantenoptik, 85748Garching, Germany Olivier Morin, M. Körber, S. Langenfeld, andG. Rempe Qubit memoriesforquantumnetworks Quantum Communication notes development the for importance tremendous a of are memories ubit unu ntok plctos I par In applications. network quantum for memories qubit photonic of opment devel- the on progresses recent our ent pres- will I requirements, two those from starting talk, In this addressed: fidelity. and efficiency be to have challenges two essentially memory, qubit a For essary. nec- is effects physical various the of trol con- and understanding thorough a ers, oth- as well as systems However,such for - system [2]. our by handled be can it how show and protocols information quantum in modes temporal photon single of role the cuss dis- will I addition, In [1]. communication quantum scale global up opening thus and 100ms than more to up time storage the extend can we how show ticular,will I References [2] O. Morinetal., inpreparation. 18-21 (2018). 12, Photon. Nature al., et Körber M. [1] Invited Talks Tue, 17:40 31 Poster Session Session A

Monday, 13:30 - 14:30

References

32 Poster Overview A Session Poster Poster No # No # Nanomechanical strings in superconducting hybrid quantum Decoherence dynamics of electron spins in an optically active 01 systems 14 quantum dot Daniel Schwienbacher �� 34 Christian Dangel, Frederik Bopp �� 39

Superconducting planar microwave resonators for high- Single atoms in crossed fiber cavities 02 sensitivity magnetic resonance applications 15 Joseph D. Christesen �� 40 Stefan Weichselbaumer �� 34 Studying the Coulomb glass phase on the Bethe lattice Non-local emergent hydrodynamics in a long-range interacting 16 Izabella Lovas �� 40 03 spin chain Alexander Schuckert �� 35 Stability of symmetries in quantum mechanics 17 Javier Cuesta �� 41 Return probability for the Anderson model on the random regu- 04 lar graph and generalized Rosenzweig-Porter random matrix New probes of the Fermi-Hubbard model ensemble 18 Annabelle Bohrdt �� 41 Giuseppe De Tomasi �� 35 Universality of local weak interactions and its application for Numerical study of the many body localization transition 19 interferometric alignment 05 Kévin Hémery �� 35 Jan Dziewior �� 42

Towards an efficient quantum memory at telecom wavelength New microscopic paradigms in the doped Fermi-Hubbard 06 Benjamin Merkel �� 36 20 model Fabian Grusdt �� 42 Towards single-shot readout of NV centers in diamond by 07 low-temperature spin-to-charge conversion Quantum key distribution with small satellites Dominik M. Irber �� 36 21 Peter Freiwang �� 43

Simulating quantum many-body dynamics on a current Quantized corner charge: Topological invariant for higher order 08 quantum computer 22 symmetry protected topological phases in the 2D Adam Smith �� 37 superlattice Bose Hubbard Model Julian Bibo �� 43 A strengthened data processing inequality for the 09 Belavkin-Staszewski relative entropy Simultaneous transmission of classical and quantum informa- Andreas Bluhm �� 37 23 tion under channel uncertainty and jamming attacks Gisbert Janßen �� 44 Quantum error-detection at low energies 10 Martina Gschwendtner �� 37 Periodically driven Sachdev-Ye-Kitaev models 24 Clemens Kuhlenkamp �� 44 Secure quantum remote state preparation of squeezed 11 microwave states Photonic crystal cavities for efficient coupling to individual Kirill G. Fedorov �� 38 25 Erbium ions Lorenz Weiss �� 44 Coupling of atomically thin semiconductors to plasmonic 12 nanoantennas Giant enhancement of Imbert Fedorov shift (Spin Hall effect Marko M. Petric �� 38 26 of light) in metals through confocal microscopy Meryem Benelajla �� 45 Understanding the spin physics of donors 13 David Vogl, Jonathan Zerhoch �� 39 Optomechanics and Quantum Optics 27 David Hoch �� 45

33 Poster Session Session A

01 Nanomechanical strings in superconducting hybrid quantum systems

Daniel Schwienbacher1,2,3, P. Schmidt1,2,3, N. Segercrantz1, M. Pernpeintner1,2,3, F. Wulschner1,2, F. Deppe1,, A. Marx1, R. Gross1,2,3, and H. Huebl1,2,3 1 Walther-Meißner-Insitut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany 2 Physik-Departement, Technische Universität München, 85748 Garching, Germany 3 Nanosystems Initiative Munich, Schellingstraße 4, 80799 München, Germany

n nano-electromechanics, quantum Here, we present two approaches for the device (type 2), where the nano-string is Imechanical phenomena can be stud- design of such a hybrid system consisting integrated into the shunt capacitance of ied in the literal sense. For example, the of a superconducting coplanar micro- a transmon qubit which itself is located coupling of nanomechanical elements wave resonator, a transmon qubit, and at the voltage antinode of the supercon- to superconducting resonators allows to a nanomechanical string resonator, for ducting coplanar waveguide resonator. cool the mechanical mode to its ground which we discuss design considerations state as well as squeeze its motion. The as well as spectroscopy data. To be spe- While device type 1 allows for the investi- preparation of mechanical (phonon) Fock cific, we present two device types: one gation of photon and phonon numbers in states comes into reach by combining the device (type 1), where the nano-string is the system, device type 2 is dedicated for circuit with a sufficiently nonlinear circuit integrated into a superconducting copla- the investigation of mechanical ground element. In this context, a superconduct- nar waveguide resonator at a voltage anti- state cooling using a transmon and the ing qubit is one obvious choice. node, while a transmon qubit is situated at initialization of phonon Fock states. another voltage antinode, and a second

Superconducting planar microwave resonators for high-sensitivity magnetic resonance applications 02

Stefan Weichselbaumer1,3, P. Natzkin1,3, C. W. Zollitsch1,3, M.Weiler1,3, M. S. Brandt2,3, R. Gross1,3, H. Huebl1,3 1 Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching 2 Walter Schottky Institut, Technische Universität München, 85748 Garching 3 Physik-Department, Technische Universität München, 85748 Garching

icrowave resonators are widely used frequency and quality factors as well as of the spin ensemble, and the linewidth of Min magnetic resonance experiments the three-dimensional microwave mag- the microwave resonator. These measure- to concentrate the magnetic field at the netic field distribution of the resonators. ments allow a single-shot measurement sample location and therefore increase Continuous-wave ESR experiments of of the coherence time T2 of the spin en- the sensitivity. This is in particular useful phosphorus donors in natSi demonstrate semble. in electron spin resonance (ESR) applica- the feasibility of our resonators for mag- tions, where one investigates paramagnetic resonance experiments. We extract netic spin ensembles. For high-sensitivity the collective coupling rate between the magnetic resonance applications, one spin ensemble and the microwave reso- References wants to optimize both the filling factor as nator and find a good agreement with well as the quality factor of the resonator our simulation results, corroborating our [1] Weichselbaumer et al., arX- in use. Three-dimensional cavities offer model approach. iv:1811.02971 (2018). excellent quality factors, but at the cost of reduced filling factors for small sample We use these planar microwave reso- [2] Weichselbaumer et al., arX- sizes. In contrast, the use of planar super- nators to investigate the dynamics of a iv:1809.10116 (2018). conducting microwave resonators enable strongly coupled 28Si:P spin ensemble at both ultra-high quality factors as well as Millikelvin temperatures [2]. In particular, large filling factors due to the small mode we use Hahn echos and observe multiple volume. unexpected echo signatures after the first conventional echo. We present experi- We present three designs for planar su- mental data within and outside the strong perconducting microwave resonators for coupling regime and discuss a model electron spin resonance (ESR) experi- predicting and corroborating the ampli- ments [1]. We implement finite element tude evolution of the echos based on the simulations to calculate the resonance echo separation time, the dephasing rate

34 Poster Session A Session

03 Non-local emergent hydrodynamics in a long-range interacting spin chain

Alexander Schuckert, I. Lovas, M. Knap Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany

hort-range interacting quantum sys- rise to effective classical Lévy flights, a scaling function smoothly covering all sta- Stems with a conserved quantity show random walk with step sizes following ble symmetric distributions as a function universal diffusive behaviour at late times a heavy-tailed distribution. We demon- of β for 0.5<β<1.5. In particular, the spin in the absence of quasiparticle excita- strate this phenomenon in a long-range autocorrelation function decays algebra- tions. We show how this universality is interacting XY spin chain, conserving the ically, with the exponent given by 1/(2β- replaced by a more general transport total magnetization Sz, at infinite tem- 1). Our findings can be readily verified process in the presence of long-range perature by employing non-equilibrium with current trapped ion experiments and interactions decaying algebraically, as r(-β), quantum field theory and semi-classical may also be observable in critical itinerant with distance r. While diffusion is recov- phase-space simulations. We find that the ferromagnets. ered for large exponents β>1.5, longer- space-time dependent spin density pro- ranged interactions with 0.5<β<1.5 give files show a self-similar behaviour, with a

Return probability for the Anderson model on the random regular graph and generalized Rosenzweig-Porter random matrix ensemble 04

Giuseppe De Tomasi, M. Amini, B. Soumya, I. M. Khaymovich, V. E. Kravtsov, A. Scardicchio Technische Universität München , 85747 Garching, Germany

e study the return probability for turn probability has a standard form, char- References Wthe Anderson model on the ran- acterized by a polynomial decay with time dom regular graph (RRG) [1] and on Gen- with periodic oscillations, which are attri- [1] Phys. Rev. B 98, 134205 (2018). eralized Rosenzweig-Porter random ma- bute of the Wigner-Dyson-like behaviour. trix ensemble (RP) [2]. Moreover, we study the full propagation [2] SciPost Phys. 6, 014 (2019). of an initially localized wave packet on We give evidence of the existence of two the RRG, showing that it can host a sub- [3] In preparation. distinct phases: a fully ergodic and non- diffusive phase [3]. ergodic one. In the ergodic phase the re-

05 Numerical study of the many body localization transition

Kévin Hémery, A. Smith, F. Pollmann Department of Physics, T42, Technische Universität München, James-Franck-Strasse 1, D-85748 Garching, Germany

he many body localization (MBL) developed DMRG-X method [1]—a matrix References Tphase of matter provides a robust al- product state method well suited to ex- ternative to thermalization and ergodicity tract excited states of MBL Hamiltonians. [1] Vedika Khemani et al. Phys. Rev. Lett. in quantum systems. It has gained consid- Thanks to this technique, we can reach 116, 247204. erable attention in the last few years due system sizes far beyond what is achiev- to its fundamental importance in the un- able using exact diagonalization tech- [2] Loïc Herviou et al. Phys. Rev. B 99, derstanding of statistical physics as well niques [2]. Motivated by a hypothesised 134205. its experimental relevance (for example thermalization avalanche process, our in cold atom systems). Despite many ef- approach is to analyse the entanglement forts, a complete understanding of the structure of these states as we approach MBL-ergodic transition is still missing. the transition. We study the transition using the recently

35 Poster Session Session A

06 Towards an efficient quantum memory at telecom wavelength

Benjamin Merkel, P. Cova Fariña, A. Reiserer MPI of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching, Germany

lobal quantum networks will re- finesse cavities that enhance the optical References Gquire efficient interfaces between depth 10000 fold. This should allow us long-lived memory nodes and photons to implement efficient quantum memo- [1] S. R. Hastings-Simon et al., Phys. Rev. at a telecommunications wavelength, ries in crystals with extremely low dop- B 78, 085410 (2008). where loss in optical fibers is minimal. In ant concentration. To facilitate cryogenic this context, ensembles of Erbium ions operation, the disturbance of mechanical doped into suited crystals are a promis- vibrations, which are abundant in closed- ing candidate, as they exhibit both an op- cycle cryostats, were minimized by an optical transition at 1.5 µm and spin lifetimes timization of the cavity mount. Second, we exceeding 100 ms [1]. Unfortunately, di- also investigate the effect of microwave pole-dipole interactions between neigh- pulses on ensembles of Erbium spins and boring Erbium ions limit the ground-state explore the potential of dynamical decou- spin coherence times and restrict the pling to increase coherence times. To this experiments to crystals with low dopant end, we have implemented a resonator concentration. This severely limits the ef- on a printed circuit board whose micro- ficiency of quantum memories. We study wave field is very homogeneous over the two approaches to overcome this chal- crystal. We will present the current status lenge: First, we have assembled high- of the mentioned experiments.

Towards single-shot readout of NV centers in diamond by low-temperature spin-to-charge conversion 07

Dominik M. Irber1, F. Kong2, F. Shi2, M. Kieschnick3, J. Meijer3, J. Du2 and F. Reinhard1 1 TU München, Walter Schottky Institut und Physik-Department, Am Coulombwall 4, 85748 München, Germany 2 Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui, 230026, PR China 3 Felix-Bloch-Institut für Festkörperphysik Abteilung Angewandte Quantensysteme, Linnéstraße 5, 04103 Leipzig, Germany

e present our recent progress in are more stable than the initial spin-state References Wimplementing an improved read- and can currently be read-out with near out scheme for the nitrogen-vacancy single-shot fidelity. [1] A. Batalov, Physical Review Letters (NV) center’s spin-state combining reso- 102, 195506 (2009). nant excitation at low temperature with Compared to the state-of-the-art read- spin-to-charge conversion. Resonant out [5], this work promises to accelerate [2] M.W. Doherty, New Journal of Physics excitation exploits that the optical exci- readout by a factor of up to 100. Besides, 13, 025019 (2011). tation spectrum at low temperature has laser power in the optical regime can be sufficiently narrow linewidths [1,2] tose- reduced by orders of magnitude. This [3] B.J. Shields, Physical Review Letters lectively address the spin-sublevels. In reduces the risk of photodamage for fu- 114, 136402 (2015). combination with a second laser pulse, ture sensing experiments with biological a spin-to-charge conversion [3,4] proto- samples. [4] X.-D. Chen, Physical Review A 7, col can be implemented, where the NV 014008 (2017). center is spin-selectively excited and con- verted to different charge-states. These [5] D.A. Hopper, Micromachines 9, 437 (2018).

36 Poster Session A Session

08 Simulating quantum many-body dynamics on a current quantum computer

Adam Smith1,2, M. Kim1, F. Pollman2, J. Knolle1 1 Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom 2 Department of Physics, T42, Technische Universität München, James-Franck-Straße 1, D-85748 Garching, Germany

niversal quantum computers are po- teractions on quantum particle transport, tion. Despite this, we are successfully able Utentially an ideal setting for simulat- as well as correlation and entanglement to demonstrate clear qualitative behav- ing many-body quantum dynamics that is spreading. Our benchmark results show iour associated with localization physics out of reach for classical digital comput- that the quality of the current machines is and many-body interaction effects. ers. We use state-of-the-art IBM quantum below what is necessary for quantitatively computers to study paradigmatic exam- accurate continuous time dynamics of ob- ples of condensed matter physics – we servables and reachable system sizes are simulate the effects of disorder and in- small comparable to exact diagonaliza-

A strengthened data processing inequality for the Belavkin-Staszewski relative entropy 09

Andreas Bluhm¹ and A. Capel² ¹ Fakultät für Mathematik, Technische Universität München, Boltzmannstr. 3, 85748 Garching, Germany ² Instituto de ciencias matemáticas (CSIC-UAM-UC3M-UCM), C/ Nicolás Cabrera 13–15, Campus de Cantoblanco, 28049, Madrid, Spain

n this work, we provide a strengthening standard f-divergences. To this end, we first focus on quantum channels which are Iof the data processing inequality for the provide two new equivalent conditions conditional expectations onto subalge- relative entropy introduced by Belavkin for the equality case of the data process- bras and use the Stinespring dilation to lift and Staszewski (BS-entropy). This extends ing inequality for the BS-entropy. Subse- our results to arbitrary quantum channels. previous results by Carlen and Vershy- quently, we extend our result to a larger nina for the relative entropy and other class of maximal f-divergences. Here, we

10 Quantum error-detection at low energies

Martina Gschwendtner1 , R. Koenig1,2, B. Sahinoglu3, E. Tang3 1 Zentrum Mathematik, Technical University of Munich, 85748 Garching, Germany 2 Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany 3 Department of Physics and Institute for Quantum Information and Matter, California Institute of Technology, Pasadena CA, 91125, USA

otivated by the close relationship this no-go result, we consider excited contains -within its low-energy eigens- Mbetween quantum error-correction, states, i.e., we use the excitation ansatz to pace- an error-detecting code with the topological order, the holographic AdS/ construct encoding maps: these yield er- same parameter scaling.All these codes CFT duality, and tensor networks, we ini- ror-detecting codes with distance Ω(n1-νν) detect arbitrary d-local (not necessarily tiate the study of approximate quantum for any νЄ(0,1) and Ω(log n) encoded qu- geometrically local) errors even though error-detecting codes in matrix product bits. This shows that gapped systems con- they are not permutation-invariant. This states (MPS). We first show that using tain - within isolated energy bands - error- suggests that a wide range of naturally open-boundary MPS to define bound- detecting codes spanned by momentum occurring many-body systems possess in- ary to bulk encoding maps yields at most eigenstates. We also consider the gapless trinsic error-detecting features.[1] constant distance error-detecting codes. Heisenberg-XXX model, whose energy These are degenerate ground spaces of eigenstates can be described via Bethe gapped local Hamiltonians. To get around ansatz tensor networks. We show that it

37 Poster Session Session A

11 Secure quantum remote state preparation of squeezed microwave states

Kirill G. Fedorov1,2, S. Pogorzalek1,2, M. Renger1,2, Q. Chen1,2, M. Partanen1, A. Marx1, F. Deppe1,2,3, and R. Gross1,2,3 1 Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany 2 Physik-Department, TU München, 85748 Garching, Germany 3 Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany

uantum communication protocols ements in order to generate propagating the von Neumann entropies. Qemploy nonclassical correlations two-mode squeezed (TMS) microwave as a resource for an efficient transfer of states acting as our quantum resource. We acknowledge support by the Excel- quantum states. As a fundamental proto- Combined with a feedforward, we use lence Cluster MCQST, the Elite Network col, remote state preparation (RSP) aims the TMS states to experimentally demon- of Bavaria through the program ExQM, at the preparation of a known quantum strate the continuous-variable RSP proto- and the European Union via the Quan- state at a remote location using classical col by preparing single-mode squeezed tum Flagship project QMiCS (Grant No. communication and quantum entangle- states at a distant location. Finally, security 820505). ment. We use flux-driven Josephson of RSP is investigated by using the con- parametric amplifiers and linear circuit el- cept of the one-time pad and measuring

Coupling of atomically thin semiconductors to plasmonic nanoantennas 12

Marko M. Petric1,2, A. Nolinder1, A. Lyamkina1, M. Kaniber1, A. V. Stier1, K. Müller2, and J. J. Finley1 1 Walter Schottky Institut and Fakultat fur Physik, Technische Universitat Munchen, Am Coulombwall 4, 85748 Garching, Germany 2 Walter Schottky Institut and Fakultat fur Electrotechnik und Informationstechnik, Technische Universitat Munchen, Am Coulombwall 4, 85748 Garching, Germany

ombining nano-optical systems with Coptically active two-dimensional materials has recently emerged as a fas- cinating topic to achieve new optical functionalities at the nanoscale [1]. In this contribution, we present investigations of light-matter interactions between transition metal dichalcogenide (TMD) monolayers and lithographically defined gold bowtie nanoantennas. By performing 3D-FDTD calculations, we tuned the design of the bowtie nanoantennas to match the dipolar resonance with the fundamental exciton transitions in a proxi-

mal MoSe2 monolayer. Fabricated bowtie nanoantennas show quality factors of Q =

5 and sub-10nm feed-gaps with estimat- system in the weak-coupling regime with

ed mode volumes as small as Vm = 2000 spectra exhibiting Fano-like behavior. Fur- nm3. Typical differential reflectance spec- thermore, we demonstrate active control References tra recorded from individual TMD-bowtie of the optical response by varying the nanostructures at room temperature re- polarization of the excitation light. The [1] D. G. Baranov et al., ACS Phot. 5, 24- veal low- and high-energy peaks sepa- methods developed in our work contrib- 42 (2017) . rated by a dip at the energy of the un- ute to on-demand realization of optimally coupled exciton. To elucidate the nature coupled TMD-nanoantenna systems that [2] X. Wu et al., Opt. Exp. 18, 23633- of characteristic spectral features, we use can be site-selectively addressed. This 23645 (2010). the coupled oscillator model [2], which type of nanostructure could pave the way result in coupling constants at zero detun- for on-chip actively controlled hybrid de- ing of g = 55 meV. This places our hybrid vices operating at elevated temperatures. 38 Poster Session A Session

13 Understanding the spin physics of donors

David Vogl, Jonathan Zerhoch, D. P. Franke and M. S. Brandt Walter Schottky Institut and Physik-Department, Technische Universität München, 85748 Garching, Germany

e present Auger-electron-detect- nuclear spin under conditions where the References Wed magnetic resonance (AEDMR) hyperfine splitting is not resolved in the experiments on phosphorus donors in optical spectrum [3]. Compared to pre- [1] A. Yang et al., Phys. Rev. Lett. 97, silicon, where the selective optical gen- vious studies, this significantly relaxes 227401 (2006). eration of donor-bound excitons is used the requirements on the sample and the for the electrical detection of the elec- experimental setup, e.g., with respect to [2] K. Saeedi et al., Science 342, 830 tron spin state [1]. Because of the long strain, isotopic purity, and temperature. (2013). dephasing times of the electron spins in The technique is also applicable to do- isotopically purified 28Si, weak micro- nors such as As, Sb or Bi with nuclear spin [3] D. P. Franke et al., Phys. Rev. Lett. 115, wave fields are sufficient for these- ex higher than 1/2, which opens up the pos- 057601 (2015). periments [2]. Implementing Auger-elec- sibility of examining the quadrupolar spin tron-detected electron nuclear double interaction and its dependence on strain [4] D. P. Franke et al., Phys. Rev. B 94, resonance (ENDOR), we further demon- in more detail [4]. 235201 (2016). strate the optically assisted control of the

Decoherence dynamics of electron spins in an optically active quantum dot 14

Christian Dangel1,3, Frederik Bopp1,3, H. J. Rojas1,3, A. Bechtold1, T. Simmet1,3, P. L. Ardelt1, D. Rauch1, F. Li4, N. A. Sinitsyn4, K. Müller2,3 and J. J. Finley1,3 1 Walter Schottky Institut and Physik Department, Technical University of Munich, Am Coulombwall 4, 85748 Garching, Germany 2 Walter Schottky Institut and Department of Electrical and Computer Engineering, Technical University of Munich, Am Coulombwall 4, 85748 Garching, Germany 3 Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany 4 Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 USA

emiconductor self-assembled quan- but three distinct stages of decoherence ends, we present our results towards re- Stum dots (QDs) offer a manifold of can be identified in the relaxation of a QD alizing a structure where the two-electron possibilities to realize interacting quan- electron spin qubit. Measurements and spin states will be all-optically prepared tum systems for quantum information simulations of the spin projection without such that the electric control of the elec- elements such as qubits, gates and spin- an external field clearly reveal an addi- tric field applied along the growth direc- photon interfaces. However, assessing tional decoherence stage at intermediate tion can be independently used to tune the suitability for applications requires a timescales [2]. The additional stage corre- the system to the “sweet spot”. Realizing detailed understanding of the decoher- sponds to the effect of coherent dephas- such a promising system requires a sys- ence dynamics and exploring ways to ex- ing processes that occur in the nuclear tematic engineering of the growth pro- tend the obtainable coherence times. spin bath itself induced by quadrupolar cess in order to precisely control parame- coupling of nuclear spins to strain-driven ters such as transition energies of the two For electron spin in QDs two basic types electric field gradients, leading to a rela- QDs and tunneling rates. of spin relaxation routes are recognized tively fast but incomplete non-monotonic in phenomenological models of deco- relaxation of the central spin polarization herence: fast ensemble dephasing due (~750ns). References to the coherent precession of spin qubits around nearly static but randomly A system which promises significantly [1] I. A. Merkulov, Al. L. Efros, and M. distributed hyperfine fields (~2ns) and a longer T2* times consists of logic singlet- Rosen, Phys. Rev. B 65, 205309 (2002). much slower process (>1μs) of irrevers- triplet qubits formed in vertically stacked ible monotonic relaxation of the spin pairs of QDs, so called QD-molecules. [2] A. Bechtold et al., Nature Physics 11, qubit polarization due to nuclear spin co- Here, a specific “sweet spot” in the ap- 1005–1008 (2015). flips with the central spin or due to other plied gate voltage can be realized in complex many-body interaction effects which the singlet-triplet energy splitting is [3] K. M. Weiss et al., Phys. Rev. Lett. 109, [1]. Here, we demonstrate experimen- in first order independent to electric and 107401 (2012). tally and theoretically that not only two magnetic field fluctuations [3]. To these 39 Poster Session Session A

15 Single atoms in crossed fiber cavities

Joseph Dale Christesen, M. Brekenfeld, D. Niemietz, and G. Rempe Max Plank Institute of Quantum Optics, Hans-Kopfermann-Str. 1, 85748 Garching

n general, to observe an interaction mode volumes. CO2 laser ablation has References Ibetween an atom and a photon, an also enabled the creation of high quality extremely large number of either are re- mirrors on nontraditional substrates in- [1] D. Hunger et al., New J. Phys. 12, quired. Cavity quantum electrodynamics, cluding the ends of optical fibers [1]. The 065038 (2010). however, provides a rich toolbox for uti- smaller dimensions of optical fiber cavi- lizing single atoms and single photons to ties also enable new cavity geometries, investigate fundamental phenomena in including coupling a single emitter to two quantum physics through an increased independent and perpendicular cavity light-matter coupling which is inversely modes. We have set up a new experiment proportional to the square root of the consisting of two crossed fiber cavities cavity mode volume. Traditional manu- which realizes this unique cavity geom- facturing processes of high-finesse cav- etry and will present measurements on ity mirrors have reached the limits of the trapped atoms coupling to both cavities reduction of the cavity mode volume, but including first results of a new quantum the introduction of mirrors fabricated by memory scheme. means of CO2 laser ablation has allowed for smaller radii of curvature and smaller

Studying the Coulomb glass phase on the Bethe lattice 16

Izabella Lovas1,2,3, C. Pascu Moca3,4, and G. Zarand3 1 Department of Physics T42, Technische Universität München, James-Franck-Straße 1, D-85748 Garching, Germany 2 Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany 3 Department of Theoretical Physics and BME-MTA Exotic Quantum Phases Research Group, Budapest University of Technology and Economics, 1521 Budapest, Hungary 4 Department of Physics, University of Oradea, 410087, Oradea, Romania

e study the Coulomb glass behav- glassy phase, and also grants us access References Wior emerging from the interplay of to the spectral function. In particular, we interactions and disorder, by examining a examine the scaling of the pseudogap [1] A. A. Pastor and V. Dobrosavljevic, model of spinless fermions at half filling at close to zero temperatures, where the Phys. Rev. Lett. 83, 4642 (1999). on the Bethe lattice [1,2]. We consider melting of the Coulomb glass is governed the limit of infinite coordination number, by the quantum fluctuations induced by [2] M. Mueller and S. Pankov, Phys. Rev. B where we combine dynamical mean field the hopping of fermions between lattice 75, 144201 (2007). theory with a Hartree-Fock approxima- sites. Turning to the spectral function, in- tion to investigate the glass phase tran- terestingly we find that a significant- cor [3] S. Bogdanovich and D. Popovic, Phys. sition, as well as the properties of the relation dip is formed around the Fermi Rev. Lett. 88, 236401 (2002). glassy phase in the presence of full rep- energy already in the high temperature lica symmetry breaking. This approxima- phase, before entering the glassy phase. tion, becoming exact at the classical limit Our results should be relevant for under- where the hopping between lattice sites standing the glassy dynamics observed in vanishes, allows us to study the opening Si inversion layers, persisting in the metal- of the Efros-Shklovskii pseudogap in the lic phase [3].

40 Poster Session A Session

17 Stability of symmetries in quantum mechanics

Javier Cuesta and M. M. Wolf Department of Mathematics, Technische Universität München, 85748 Garching, Germany

he presence of symmetries in quan- Hilbert space admits a weak linear ap- References Ttum mechanics allows in many cases proximation, i.e. one relative to any fixed to obtain exact solutions that is difficult observable. Furthermore, we prove that a [1] E. P. Wigner, “Gruppentheorie und to conceive a theory without them. In this linear approximation that is close in norm ihre Anwendung auf die Quanten- series of work [2,3], we study how almost- and independent of the dimension of the mechanik der Atomspek-tren,” Fredrik symmetries can be approximated by exact underlying Hilbert space does not exist in Vieweg und Sohn, pp. 251-254 (1931). symmetries and provide bounds on the general. On the other hand, we present a quality of these approximations. On the new characterization of Gaussian bosonic [2] J. Cuesta, M. M. Wolf, “Are almost- one hand, we study the linear stability of states - an ubiquitous set of states in con- symmetries almost linear?” quant- the celebrated Wigner theorem [1] which tinuous quantum information- which has a ph,arxiv/1812.10019 (2018). tell us how we mathematically represent simple symmetry interpretation. We show symmetries in quantum mechanics. More how stable is this symmetry characteriza- [3] J. Cuesta, “A stable quantum precisely, we show [2] that any transfor- tion when the underlying conditions are Darmois-Skitovich theorem”, math- mation that preserves transition probabili- almost satisfied [3]. ph,arxiv/1902.05298 (2019). ties up to an additive error in a separable

New probes of the Fermi-Hubbard model 18

Annabelle Bohrdt, F. Grusdt, C. S. Chiu, G. Ji, M. Xu, D. Greif, M. Greiner, E. Demler, M. Knap Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA

he phase diagram of the Fermi- dimensions and are able to explain our References THubbard model and its connection findings in the framework of geometric to high-temperature superconductivity string theory. [1] F. Grusdt et al., Microscopic spinon- have been the subject of a vast amount chargon theory of magnetic polarons in of theoretical and experimental stud- We furthermore compare geometric the t-J model. arXiv:1901.01113. ies in the past decades. Here, we pres- string theory predictions for spin corre- ent recent results motivated by the new lation functions as well as string patterns [2] C.S. Chiu et al., String patterns perspective quantum gas microscopes at finite temperature and finite doping to in the doped Hubbard model. arX- provide. Our theoretical approach, the experimental data of a cold atom experi- iv:1810.03584. geometric string theory, describes doped ment and find remarkable agreement [2]. holes moving in an AFM environment as For an unbiased comparison of theories [3] A. Bohrdt et al., Classifying Snapshots meson-like bound states of spinons and and experiment, we apply machine learn- of the Doped Hubbard Model with Ma- chargons [1]. Matrix product state based ing to classify experimental data at finite chine Learning. arXiv:1811.12425. simulations of the ground state show doping into different theoretical catego- convincing evidence for this scenario. ries in order to determine which theory We numerically study the dynamics of a describes the system best on the micro- single hole created in the ground state for scopic level [3]. a dimensional crossover from one to two

41 Poster Session Session A

19 Universality of local weak interactions and its application for interferometric alignment

Jan Dziewior1,2, L. Knips1,2, D. Farfurnik3, K. Senkalla1,2, N. Benshalom3, J. Efroni3, J. Meinecke1,2, S. Bar-Ad3, H. Weinfurter1,2, and L. Vaidman3 1 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany 2 Department für Physik, Ludwig-Maximilians-Universität, 80797 München, Germany 3 Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978, Israel

ostselection of quantum systems is this location is affected in the same man- References Pused in many quantum applications ner, in this sense the effective presence of and can lead to intricate novel effects. The the particle can be seen as altered. [1] Y. Aharonov, L. Vaidman in, Time in two-state vector formalism developed by Quantum Mechanics, J. G. Muga, R. Sala Aharonov and Vaidman [1] represents We demonstrate our findings experi- Mayato, I. Egusquiza ed. (2008). and elegant and intuitive way to describe mentally by considering pre- and postse- pre- and postselected quantum systems. lected photons passing through a Mach- [2] Y. Aharonov, D. Z. Albert, L. Vaidman, Its key element are weak values of observ- Zehnder interferometer. By characterizing “How the result of a measurement of ables, which are empirically accessible the effects due to various, different in- a component of the spin of a spin-1/2 via weak measurements and can lead to teractions in one of the interferometers particle can turn out to be 100”, Phys. Rev. results that lie far outside the usual spec- arms, we are able to show how different Lett. 60, 1351 (1988). trum of the measured observables [2]. degrees of freedom are influenced in the This property of weak values became the same manner. [3] O. Hosten and P. Kwiat, “Observation basis of several successful applications of the Spin Hall Effect of Light via Weak in precision measurement techniques [3] Apart from this foundational result our Measurements”, Science 319, 787 (2008). and further applications still emerge [4]. findings lead to a novel, simple, andef- ficient alignment technique for interfer- [4] G. Chen, N. Aharon, Y.-N. Sun, Z.-H. In this work we investigate the fundamen- ometers, which harnesses the benefits of Zhang, W.-H. Zhang, D.-Y. He,J.-S. Tang, tal properties of pre- and postselected weak value amplification and the fact that X.-Y. Xu, Y. Kedem, C.-F. Li, G.-C. Guo, systems and show both theoretically and weak values can be complex in general. “Heisenberg-scaling measurement of the experimentally that the weak value of lo- Based on this, the phase dependence of single-photon Kerr non-linearity using cal projection represents a universal de- the image on only a single detector in the mixed states”, Nature Communications 9, scription of how an effect due to any in- output of an interferometer allows to ex- 93 (2018). teraction of the particle is modified. Since tract misalignment parameters. the totality of the particle’s interactions at

New microscopic paradigms in the doped Fermi-Hubbard model 20

A. Bohrdt1, E. Demler2, M. Knap1, and Fabian Grusdt1 1Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany 2Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

he interplay of mobile dopants with ulations. The trial wavefunction is used to References Tanti-ferromagnetic spin correlations analyze the spectral weight, and we argue is at the heart of high-temperature su- that it provides indications that spinons [1] F. Grusdt, A. Bohrdt, and E. Demler, perconductivity. Here we present a mi- have fermionic statistics. Our microscopic arXiv:1901.01113, PRB (in press). croscopic trial wavefunction describing model explains the observations of string individual dopants as spinon-chargon patterns [2,3] and the dressing cloud of [2] C.S. Chiu et al., arXiv:1810.03584. composites [1]. We derive the correla- magnetic polarons [4] in recent measure- tions of the charges with their spin envi- ments performed with ultracold atoms in [3] A. Bohrdt et al., arXiv:1811.12425. ronment and reveal short-range hidden optical lattices. Our approach can be ap- string order, which manifests in genuine plied at finite doping and paves the way [4] J. Koepsell et al., arXiv:1811.06907. higher-order correlations developing for a microscopic description of the exotic around the dopants and can be directly metallic phases in strongly correlated cu- observed in state-of-the-art quantum sim- prate compounds.

42 Poster Session A Session

21 Quantum key distribution with small satellites

Ö. Bayraktar4, Peter Freiwang3, D. Garbe1, M. Grünefeld6, R. Haber1, L. Knips5, C. Marquardt4, L. Mayr3, F. Moll2, J. Pudelko4, B. Rödiger2, W. Rosenfeld3, K. Schilling1, C. Schmidt2 and H. Weinfurter3, 5 1 Center for Telematics (ZfT), Würzburg, Germany 2 German Aerospace Center (DLR) IKN, Oberpfaffenhofen, Germany 3 Ludwig-Maximilian-University (LMU), Munich, Germany 4 Max Planck Institute for the Science of Light (MPL), Erlangen, Germany 5 Max Planck Institute of Quantum Optics (MPQ), Garching, Germany 6 OHB System AG, Oberpfaffenhofen, Germany

KD to satellites can enable global Together with a second quantum payload References Qsecure communication. After the to evaluate CV-QKD [3] and quantum ran- first successful demonstration by the Chi- dom number generation [4], this mission [1] S. Liao et al., Phys. Rev. Lett. 120, nese satellite MICIUS [1], the question will study the feasibility of cost effective 30501 (2018). arises how small a satellite can be de- QKD with nano-satellites in low-earth-or- signed. We show our concept for a BB84 bits (~ 500 km altitude). In the first phase, [2] G. Vest et al., IEEE JSTQE 21, 3 (2014). QKD payload [2] for the nano-satellite the satellite with a planned size of only mission QUBE. Faint laser pulses from 30x10x10 cm3 will use an optical terminal [3] T. C. Ralph, Phys. Rev. A 61, 010303 four VCSELs at 850 nm are polarized us- (OSIRIS - Optical Space Infrared Down- (1999). ing an array of polarizer foils and focused link System) with an aperture of 20 mm into a waveguide chip, which couples the for downlink to the optical ground station [4] C. Gabriel et al., Nature Photonics 4, four input modes into a single mode fiber. with a planned telescope size of 80 cm to p: 711–715 (2010). The optical QKD-unit will be hermetically achieve high coupling efficiency. sealed and mounted onto a 9x9 cm2 PCB.

Quantized corner charge: Topological invariant for higher order symmetry protected topological phases in the 2D superlattice Bose Hubbard Model 22

Julian Bibo, I. Lovas, F. Grusdt, and F. Pollmann Technical University of Munich, Germany

opological insulators combine an in- there is also a global U(1) symmetry as- References Tsulating bulk with gapless edge states sociated with particle number conserva- at their boundaries. Recently, higher-or- tion. We show that the 2D SL BHM can [1] Wladimir A. Benalcazar et al., Science der topological insulators (HOTI’s) have realize two inequivalent HOTI’s as long as 357, 61 (2017). been discovered. In contrast to conven- the bulk stays incompressible. We argue tional topological insulators, an n-th high- that the topologically inequivalent classes [2] Oleg Dubinkin et al. , er-order topological insulator in d dimen- can be labelled by the fractional part of arXiv:1904.09932v2. sions hosts (d-n) dimensional topological the corner charge which is quantized to protected gapless boundary modes, but Q=0 or Q=0.5. The fractional part of the [3] Steve White , Phys.Rev. (d-1) dimensional gapped boundary corner charge cannot change as long as Lett.69(1992),2863. states. The gapless boundary states are any perturbation respects the symme- protected by symmetries [1]. These fea- tries and does not close the bulk gap. To tures even survive in the presence of in- support our analytical arguments, we use teractions [2]. the density renormalization group ansatz (DMRG) [3] on a finite 2D system, where Here we study the 2D superlattice (SL) we determine the phase diagram of the Bose Hubbard (BHM) at half-filling on a 2D SL BHM and calculate the full counting square lattice with open boundaries at statistic of the fractional part of the corner various values for the on-site interaction charge Q. strength. Beside the spatial C4 symmetry

43 Poster Session Session A

Simultaneous transmission of classical and quantum information under channel uncertainty and 23 jamming attacks

H. Boche, Gisbert Janßen, S. Saeedinaeeni Lehrstuhl für Theoretische Informationstechnik, Technische Universität München, 80290 München

e derive universal codes for simul- mission through quantum channels. We ous transmission of classical messages Wtaneous transmission of classical show these codes to be optimal by giving and entanglement. These include cases messages and entanglement through a multi-letter characterization of regions where the malignant jammer present in quantum channels, possibly under the corresponding to capacity of compound the arbitrarily varying channel model is attack of a malignant third party. These quantum channels for simultaneously classical (chooses channel states of the codes are robust to different kinds of transmitting and generating entangle- product form) and fully quantum (is ca- channel uncertainties. To construct such ment with classical messages. In addition, pable of general attacks not necessarily universal codes, we invoke and general- we give dichotomy statements in which of the product form). ize the properties of random codes for we characterize the capacity of arbitrarily classical and quantum message trans- varying quantum channels for simultane-

Periodically driven Sachdev-Ye-Kitaev models 24

Clemens Kuhlenkamp and M. Knap Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany and Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany

eriodically driven quantum matter can (SYK)-model, which realizes a crossover quasi-particles in the heavy FL obstructs Prealize exotic dynamical phases. In or- from a heavy Fermi liquid (FL) to a non- heating and thermalization over compar- der to understand how ubiquitous and ro- Fermi liquid (NFL) at a tunable energy atively long time scales. Prethermal high- bust these phases are, it is pertinent to in- scale. Developing an exact field theoretic frequency dynamics and possible experi- vestigate the heating dynamics of generic approach, we determine two distinct re- mental realizations of non-equilibirum interacting quantum systems. Here we gimes in the heating dynamics. While the SYK physics are discussed as well. study the thermalization in a periodically- NFL heats exponentially and thermalizes driven generalized Sachdev-Ye-Kitaev rapidly, we report that the presence of

25 Photonic crystal cavities for efficient coupling to individual Erbium ions

Lorenz Weiss, A. Gritsch, T. Aladjidi, and A. Reiserer Max Planck Institute of Quantum Optics, 85741 Garching, Germany

rbium ions trapped in suited host guides that can then be transferred to a References Ecrystals are promising candidates suited substrate material1. At cryogenic for large-scale quantum networks since temperature, we thus expect to shorten [1] D. Hunger et al., New J. Phys. 12, they can combine second-long ground the radiative lifetime of the optical transi- 065038 (2010). state spin coherence times with coherent tions by more than three orders of magni- optical transitions at telecommunication tude via the Purcell effect. This will enable wavelengths. Unfortunately, the extreme- deterministic interactions between indi- ly long lifetime of the excited state (10 ms) vidual spins and single telecom photons, makes it difficult to spectrally resolve and opening unique prospects for the real- control individual ions in order to harness ization of entanglement between spins them for quantum networks. over distances exceeding 100 km. We will present simulations and the current sta- To overcome this challenge, we design tus of the experiment towards single-ion and fabricate Photonic Crystal Cavities spectroscopy and control. (PCC) on one-dimensional silicon wave- 44 Poster Session A Session

26 Giant enhancement of Imbert Fedorov shift (Spin Hall effect of light) in metals through confocal microscopy

Meryem Benelajla1,2, E. Kamman1, and K. Karrai1 1 attocube systems AG, Eglfinger Weg 2, 85540 Haar bei München 2 LPCNO-INSA-CNRS-UPS, 135 Av. Rangueil, 31077 Toulouse, France

onfocal microscope is widely used high polarization extinction ratio of 109 References Cin quantum optics for studying reso- was reached using a mirror reflectivity of nant fluorescence properties of semicon- a linearly polarized Gaussian laser beam. [1] T. Kaldewey et al. Nat. Phot. 12, 68-72 ductor quantum dots [1], transition metal Whereas the polarization extinction ratio (2018). dichalcogenides (TMD) monolayers [2], of a transmitted light through two crossed etc… . polarizers is limited to only 105 -106 [2] A. Neumann et al. Nat. Nanotech. 12, range. This unexpected enhancement is 329–334 (2017). Such an experiment requires a high po- due to Imbert Fedorov shift (Spin Hall ef- larization rejection of the strong excita- fect of light) which manifests itself when a tion laser beam. However, a confocal light beam reflects at air-metal interface. microscope contains multiple depolar- izing optical elements (like mirrors and With these investigations based on a beam splitters) that makes the detection single mirror reflectivity, we intend to proof resonance fluorescence challenging. vide progress towards a high-polarization To overcome this challenge, we have ex- extinction confocal microscope based on plored the limits of laser rejection with a compensated two-mirror arrangement transmitted and reflected light through as well as compensated beam splitter ar- two crossed polarizers. In particular, a rangement.

Optomechanics and Quantum Optics 27

David Hoch1,2,3, Burak Yildiz1, Christopher Waas1, Julia Lamprich1, Luis Rosendahl1, Xiaohe Bai1, Menno Poot1,2,3 ¹EQT, Department of Physics, Technical University of Munich, James-Franck-Str. 1, 85748 Garching ²Institute for Advanced Study, Lichtenbergstraße 2a, 85748 Garching 3Munich Center for Quantum Science and Technology, Schellingstr. 4, 80799 Munich

ur group focuses on Quantum field that we focus on is optomechanics. optimizing the nanofabrication tech- OTechnologies. We make chips us- When such devices are cooled to their niques. Two new vacuum chambers for ing state-of-the-art nanofabrication tech- quantum ground state they become optomechanical studies are currently set niques to study quantum effects in a quantum mechanical objects. These de- up and will allow measurements on mi- variety of systems. One main topic is in- vices will be based on photonic and pho- crometer scale membranes and double tegrated quantum optics, where photonic nonic crystal cavities where confinement clamped bars containing both photonic chips with functionality to generate, ma- and coupling between phonons and pho- and phononic crystals. We also perform nipulate, and detect single photons are tons takes place. We are currently fabri- device simulations to predict designs that designed, made, and measured. Another cating and measuring our first chips while are promising to fabricate and study.

45 Poster Session Session B

Tuesday, 13:30 - 14:30

References

46 Poster Overview B Session Poster Poster No # No # Secure quantum remote state preparation of squeezed Single-photon distillation with a cavity QED system 28 microwave states 41 Stephan Welte �� 53 Michael Renger �� 48 Quantum gas microscopy of Rydberg macrodimers Planar scanning probes 42 Simon Hollerith �� 53 29 Paul Weinbrenner �� 48 MBL to diffusive phase transition in the strongly coupled Towards quantum simulation with 23Na40K molecules in 43 disordered t-V chain 30 optical lattices Daniel Hetterich �� 53 Marcel Duda �� 49 In-plane anisotropy of the photon-helicity induced linear Hall Quantum engineering taken to the limits of quantum 44 effect in few-layer WTe 2 31 systems theory Jonas Kiemle �� 54 Thomas Schulte-Herbrüggen �� 49 Magnetic polarons and dynamical spin-charge separation Quantum electronic circuit simulation of generalized 45 under the microscope 32 sine-Gordon models Joannis Koepsell �� 54 Ananda Roy �� 50

Hybridized indirect excitons in MoS2/WS2 heterobilayers High-finesse tunable cavity on a closed-cycle cryostat 46 Florian Sigger �� 55 33 Samarth Vadia �� 50 Quantum optoelectronics in materials with topological order A sustainable sub-Kelvin cooling technology for quantum 47 Christoph Kastl �� 55 34 electronics Tomek Schulz �� 50 Interorbital interactions in Yb-171 48 Giulio Pasqualetti �� 56

Floquet approach to Z2 lattice gauge theories with ultracold 35 atoms in optical lattices Bridging the THz gap: Toward ultrafast coherent on-chip Christian Schweizer �� 51 49 electronics up to 10 THz Fernandez Noelia �� 56 Symmetries of Liouvillians for Markovian dynamics and their 36 relation to quantum information protection Exploring mobility edges and many-body localization in a 1D Martin Seltmann �� 51 50 quasiperiodic optical lattice Thomas Kohlert �� 57 Ergodicity-breaking arising from Hilbert space fragmentation in 37 dipole-conserving Hamiltonians Towards a suburban quantum network link Pablo Sala �� 51 51 Robert Garthoff, Wei Zhang �� 57

Towards quantum simulation of light-matter interfaces with Lattice-trapped lithium as tunable Floquet matter 38 strontium atoms in optical lattices 52 David M. Weld �� 58 Jan Trautmann �� 52

Site-selectively generated photon emitters in monolayer MoS2 Reachability in infinite-dimensional unital open quantum 53 via helium ion irradiation 39 systems with switchable GKS-Lindblad generators Lukas Sigl �� 58 Frederik vom Ende �� 52 Trions in two-dimensional semiconductors - implications for Probing many-body correlations in Fermi gases using Rydberg 54 exciton-polaron physics 40 excitations Christian Fey �� 59 Marcel Wagner �� 52 Emergent Glassy Dynamics in a Quantum Dimer Model 55 Johannes Feldmeier �� 59

47 Poster Session Session B

28 Secure quantum remote state preparation of squeezed microwave states

Michael Renger1,2, S. Pogorzalek1,2, K.G. Fedorov1,2, Q.-M. Chen1,2, M. Partanen1, A. Marx1, F. Deppe1,2,3 and R. Gross1,2,3 1 Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany 2 Physik-Department, TU München, 85748 Garching, Germany 3 Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 Munich, Germany

uantum communication protocols squeezed (TMS) microwave states acting References Qemploy nonclassical correlations as our quantum resource. Combined with as a resource for an efficient transfer of a feedforward, we use the TMS states to [1] S.Pogorzalek et al., Nat. Commun., quantum states. As a fundamental proto- experimentally demonstrate the contin- doi:10.1038/s41467-019-10727-7, col, remote state preparation (RSP) aims at uous-variable RSP protocol by preparing arXiv:1902.00453 (2019). the preparation of a known quantum state single-mode squeezed states at a distant at a remote location using classical com- location [1]. Finally, security of RSP is in- munication and quantum entanglement. vestigated by using the concept of the We use flux-driven Josephson parametric one-time pad and measuring the von amplifiers and linear circuit elements in Neumann entropies. order to generate propagating two-mode

Planar scanning probes 29

S. Ernst1,2, Paul Weinbrenner1, G. Braunbeck1, D. Irber1, F. Reinhard1 1 Walter Schottky Institut and Physik-Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany 2 Department of Physics, ETH Zurich, Otto Stern Weg 1, 9093 Zurich, Switzerland

canning probe microscopy (SPM) is probe parallel to a planar sample at a References Straditionally based on very sharp tips, distance of few tens of nanometers. The where the small size of the apex is critical core element of our scheme are optical [1] A. Finkler et al., Nano Letters 10, 1046 for resolution, as in for example atomic far-field techniques to measure both dis- (2010). force microscopy. This paradigm is about tance and tilt between the two surfaces of to shift, since a new generation of planar probe and sample with 1 nm position and [2] M. J. Yoo et al., Science 276, 579 probes, such as SQUIDs [1], scanning sub-1 mrad tilt resolution. (1997). SETs [2] and nitrogen-vacancy (NV) color centers in diamond [3, 4], promises to im- We use shallow NV centers at the planar [3] G. Balasubramanian et al., Nature 455, age hitherto inaccessible quantities such surface of a bulk diamond as scanning 648 (2008). as very small magnetic and electric fields. probes. This can simultaneously lower the So far, much effort is put into fabricating fabrication complexity, improve the sen- [4] P. Maletinsky et al., Nature nanotech- these planar sensors on tip-like struc- sor quality and reduce the sensor-sample nology 7, 320 (2012). tures, to be compatible with traditional distance compared to existing tip-based SPM techniques and to bring the sensor schemes. Employing the optical far-field [5] S. Ernst et al., ACS Photonics 6, 327 close to the sample surface. This poses a measurements as a feedback signal we (2019). significant engineering challenge, which demonstrate scanning near-field optical is mastered by only a few groups. microscopy of plasmonic modes in silver nanowires by a single NV center [5]. On this poster, we present a novel, tipless approach - a technique to scan a planar

48 Poster Session B Session

30 Towards quantum simulation with 23Na40K molecules in optical lattices

Marcel Duda, R. Bause, X.-Y. Chen, I. Bloch and X.-Y. Luo Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

ltracold polar molecules are prom- lar molecules. Additionally, we observed References Uising for studying quantum many- density-dependent decoherence mani- body physics and as scalable quantum fested by the molecules’ dipolar char- [1] K.K. Ni et al., Chem. Sci., 2018,9, computers [1]. Strong dipolar interactions acter and we demonstrated a rotation- 6830-6838 (2018). and long single-particle lifetimes make it dependent dipole trap that can be tuned feasible to observe exotic phases of mat- between magic, tune-out, and anti-magic [2] D. Peter et al., Phys. Rev. Lett. 109, ter [2]. by changing the laser detuning. 025303 (2012).

We have developed a few new tools to For quantum simulation, it is still challeng- [3] F. Sesselberg et al., Phys. Rev. Lett. manipulate the rotational states of our ing and necessary to produce a degener- 121, 253401 (2018). ground state molecules. The rotational ate cloud of polar molecules. With our re- structure is particularly important for con- cent upgrade to the atomic transport, we trolling the mediated interactions but can create 105 deeply degenerate atoms also adversely couples to the trapping of Na and K. It brings us to a regime where light field. We disentangle this problem we could produce a low-entropy cloud of by using a spin-decoupled magic trap polar molecules by magnetically associat- [3] which extends the coherence time of ing atoms into Feshbach molecules and rotational states by one order of magni- subsequently transferring them into the tude to about 10 ms in a bulk gas of po- rovibronic ground state.

Quantum engineering taken to the limits of quantum systems theory 31 V. Bergholm1, W. Wieczorek2, F. vom Ende1, R. Zeier1, M. Keyl3, and Thomas Schulte-Herbrüggen1 1 Department of Chemistry, Technical University of Munich (TUM), Germany 2 Dept. of Nanoscience and Nanotechnology, Chalmers University, Gothenburg, Sweden 3 Centre for Complex Quantum Systems, FU Berlin, Germany

uantum optimal control is often key Our recent proposal [5] for an optome- References Qto exploiting the full potential of ex- chanical oscillator extended by a two- perimental set-ups pertinent to quantum level atom perfectly illustrates these [1] J.P. Dowling and G. Milburn, Phil. emerging technologies [1,2]. principles: without breaking the system Trans. R. Soc. Lond. A 361, 1655 (2003). symmetries of the optomechanical oscil- We sketch a unified comprehensive Lie lator one can only interconvert within the [2] S.J. Glaser et al., Eur. Phys. J. D 69, frame for quantum systems theory [3,4], equivalence class of states of the same 279 (2015). where symmetries and conservation laws Wigner negativity. Coupling to the atom are now in a quantum Noether-type 1:1 breaks the symmetry and thus allows to [3] T. Schulte-Herbrüggen, G. Dirr, and R. correspondence. Thus, one gets a full as- cross between these classes, e.g., from Zeier, Open Syst. Inf. Dyn. 24, 1740019 sessment of controllability, observability, Gaussian states to non-classical ones. (2017). and accessibility in quantum engineering. We now see which symmetries to break for The example thus elucidates guiding [4] T. Schulte-Herbrüggen, R. Zeier, M. more control and we show how to apply principles for quantum technologies 2.0. Keyl and G. Dirr, in: Quantum Information optimal control to exploit quantum dynam- from Foundations to Quantum Technol- ics within the enlarged accessible territory. ogy Applications, D. Bruß and G. Leuchs, Eds., VCH, pp 607-641 (2019).

[5] V. Bergholm, W. Wieczorek, T. Schulte- Herbrüggen, and M. Keyl, Quantum Sci. Technol. 4, 034001 (2019).

49 Poster Session Session B

32 Quantum electronic circuit simulation of generalized sine-Gordon models

Ananda Roy and H. Saleur Department of Physics, T42, Technische Universität München, 85748 Garching, Germany Institut de Physique Théorique, Paris Saclay University, CEA, CNRS, F-91191 Gif-sur-Yvette, France

nvestigation of strongly interacting, non- to many multi-field QFT-s. The primary References Ilinear quantum field theories (QFT-s) re- goal of this work is to investigate differ- mains one of the outstanding challenges ent thermodynamic properties of the [1] A. Roy and H. Saleur, arXiv of modern physics. Here, we describe double sine-Gordon model and propose 1902.09530 (2019). analog quantum simulators for nonlinear experiments that can capture its subtle QFT-s using mesoscopic superconduct- quantum integrability. First, we analyti- ing circuit lattices. Using the Josephson cally compute the mass-spectrum and the effect as the source of nonlinear interac- ground state energy in the presence of an tion, we investigate generalizations of external `magnetic' field using Bethe an- the quantum sine-Gordon model. In par- satz and conformal perturbation theory. ticular, we consider a two-field general- Second, we calculate the thermodynamic ization, the double sine-Gordon model. Bethe ansatz equations for the model and In contrast to the sine-Gordon model, this analyze its finite temperature properties. model can be purely quantum integrable, Third, we propose experiments to verify when it does not admit a semi-classical the theoretical predictions. description - a property that is generic

High-finesse tunable cavity on a closed-cycle cryostat 33

Samarth Vadia1,2, C. Dal Savio1 , A. Högele2 , K. Karrai1 1 attocube systems AG, Eglfinger Weg 2, D-85540 Haar bei München, Germany 2 Fakultät für Physik, Munich Center for Quantum Science and Technology (MCQST) and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, D-80539 München, Germany

he light-matter interactions in a solid- teraction with individual quantum emitter References Tstate based quantum emitter com- over large areas [1 - 3]. We will show our bined with an optical cavity is a vital tool recent progress towards achieving high- [1] T. Steinmetz et al. Applied Physics Let- for realization of quantum technologies, Finesse stable cavity at low temperature ters 89, 111110 (2006). as well as fundamental studies in field in a closed-cycle cryostat integrated with of cavity quantum electrodynamics. A an optical table. We will discuss various [2] D. Hunger et al. New Journal of Phys- promising platform has emerged based aspects of setup, particularly mechanical ics 12 (6), 065038 (2010). on Fabry-Perot cavity combined with ca- stability and show recent measurements pability for spectral and spatial tuning, characterizing the performance of the [3] R. J. Barbour et al. Journal of Applied which enables tuning cavity resonance setup. Physics 110, 053107 (2011). for effective photon confinement and in-

34 A sustainable sub-Kelvin cooling technology for quantum electronics

A. Regnat1,2, J. Spallek1,2, K. Eibensteiner1,2, Tomek Schulz1,2, C. Duvinage1, N. Huber1, C. Burger1, A. Tong1 und C. Pfleiderer1 1 Physik-Department, Technical University of Munich, Germany 2 kiutra GmbH, Munich, Germany

ooling devices providing tempera- and detectors. Commercially available erator for the cryogen-free, continuous Ctures well below 1 K are a key prereq- state-of-the art cooling solutions require generation of sub-Kelvin temperatures uisite for modern research and develop- typically the rare and costly helium iso- based on prevalent and affordable solid- ment, e.g., in materials science, quantum tope, helium-3. Here we present a versa- state cooling media. electronics and the cooling of sensors tile and compact demagnetization refrig-

50 Poster Session B Session

Floquet approach to Z lattice gauge theories with ultracold atoms in optical lattices 35 2

Christian Schweizer, F. Grusdt, M. Berngruber, L. Barbiero, E. Demler, N. Goldman, I. Bloch and M. Aidelsburger Fakultät für Physik, Ludwig-Maximilians-Univeristät München, 80799 Munich, Germany

2 lattice gauge theories (LGTs) are of atoms with strong on-site interactions in ideal Z2 LGT. We reveal challenges that Zhigh interest in condensed matter an optical two-site potential together with arise due to symmetry-breaking terms, physics and topological quantum com- resonant periodic driving. For particular which may be relevant for any experimen- putation. The investigation of strongly-in- driving parameters, the effective Floquet tal implementation, and outline potential teracting regimes, however, is especially Hamiltonian exhibits Z2 symmetry. We pathways to overcome them. The results challenging and in general difficult to ac- study the dynamics of the system for dif- provide important insights for studies of cess with conventional numerical meth- ferent initial states and find that it is well LGTs based on Floquet techniques and ods. Here, we take a first step using ana- described by a full time-dependent de- the two-site model constitutes a minimal log quantum simulations and present an scription. Moreover, it is non-trivial due instance for extended LGTs coupled to approach to realize Z2 LGTs. We use a two- to the imposed gauge constraints and matter. component mixture of ultracold bosonic in agreement with predictions from the

Symmetries of Liouvillians for Markovian dynamics and their relation to quantum information protection 36

N. Schuch1, T. Schulte-Herbrüggen2, and Martin Seltmann3 1 Max Planck Institute of Quantum Optics, 85748 Garching, Germany 2 Department of Chemistry, TU Munich, 85748 Garching, Germany 3 Department of Physics, TU Munich, 85748 Garching, Germany

nvariant or decoherence-free subspaces Within the setting of dissipative processes We present new results concerning the I(DFS) as well as the more general con- modeled by quantum dynamical semi- connection between these subspaces cept of noiseless subsystems are among groups, we explore the role of symmetries and properties of the Lindbladians, con- various schemes devised for the stabiliza- characterized by the commutants to the cluding with several applications. tion of quantum information which can be Lindbladian semigroup generators and treated in a unified algebraic framework. their relation to DFS and fixpoint spaces.

37 Ergodicity-breaking arising from Hilbert space fragmentation in dipole-conserving Hamiltonians

Pablo Sala, T. Rakovszky, R. Verresen, M. Knap, F. Pollmann Department of Physics, Technical University of Munich, 85748 Garching, Germany Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, D-80799 München, Germany

e show that the combination of infinite temperature auto-correlation sat- the system still has exponentially many in- Wcharge and dipole conservation- urates to a finite value---showcasing non- variant subspaces, but they are no longer --characteristic of fracton systems---leads thermal behavior. The absence of ther- sufficient to avoid thermalization for typi- to an extensive fragmentation of the Hil- malization is identified as a consequence cal initial states. More generally, for any bert space, which in turn can lead to a of the \emph{strong fragmentation} of finite range of interactions, the system still breakdown of thermalization. As a con- the Hilbert space into exponentially many exhibits non-thermal eigenstates appear- crete example, we investigate the out-of- invariant subspaces in the local Sz basis, ing throughout the entire spectrum. We equilibrium dynamics of one-dimensional arising from the interplay of dipole con- compare our results to charge and dipole spin-1 models that conserve charge (total servation and local interactions. Second, moment conserving random unitary cir- Sz) and its associated dipole moment. we extend the model by including four- cuit models for which we reach identical First, we consider a minimal model includ- site terms and find that this perturbation conclusions. ing only three-site terms and find that the leads to a \emph{weak fragmentation}:

51 Poster Session Session B

38 Towards quantum simulation of light-matter interfaces with strontium atoms in optical lattices

Jan Trautmann, A. Heinz, A. J. Park, E. Staub, R. Haindl, N. Šantić, I. Bloch, and S. Blatt Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

n the last two decades, quantum simu- have also started to take advantage of ume and state-dependent optical lattices Ilators based on ultracold atoms in op- optical lattices by trapping alkaline earth to emulate strongly-coupled light-matter- tical lattices have successfully emulated metal atoms such as Sr, and interrogating interfaces in parameter regimes that are strongly correlated condensed matter them with precision and accuracy at the unattainable in real photonic systems. We systems. With the recent development of 10-18 level. Here, we report on progress also report on a narrow-line magneto-op- quantum gas microscopes, these quan- towards a new quantum simulator that tical trapping technique that outperforms tum simulators can now control such sys- combines quantum gas microscopy with standard techniques in terms of speed, tems with single-site resolution. Within optical lattice clock technology. We aim to robustness, and capture fraction. the same time period, atomic clocks trap ultracold Sr atoms in large-mode-vol-

Reachability in infinite-dimensional unital open quantum systems with switchable GKS-Lindblad generators 39

Frederik vom Ende1, G. Dirr2, M. Keyl3 and T. Schulte-Herbrüggen1 1TU Munich, 85748 Garching, Germany 2 University of Würzburg, 97074 Würzburg, Germany 3 Freie Universität Berlin, 14195 Berlin, Germany

n quantum systems theory one of the many bounded control Hamiltonians al- References Ifundamental problems boils down to: lowing for (at least) piecewise constant given an initial state, which final states control amplitudes plus a bang-bang [1] F. vom Ende et al., arXiv:1902.03085 can be reached by the dynamic system in switchable noise term in GKS form (gen- (2019). question? erated by some compact V).

Here we consider infinite dimensional Generalizing standard majorization re- open quantum dynamical systems follow- sults from finite to infinite dimensions, we ing a unital Kossakowski-Lindblad mas- show that such bilinear quantum control ter equation extended by controls. More systems allow to approximately reach any precisely, their time evolution shall be target state majorized by the initial one as governed by an inevitable (potentially un- up to now only has been known in finite bounded) Hamiltonian drift term, finitely dimensional analogues.

40 Probing many-body correlations in Fermi gases using Rydberg excitations

Marcel Wagner¹,², H. R. Sadeghpour³, T. C. Killian⁴, R. Schmidt¹,² ¹ Max Planck Institute of Quantum Optics, Hans-Kopfermann-Straße 1, 85748 Garching, Germany ² Munich Center for Quantum Science and Technology, Schellingstraße 4, D-80799 München, Germany ³ ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA ⁴ Department of Physics & Astronomy and Rice Center for Quantum Materials, Rice University, Houston, TX 77251, USA

e investigate correlation functions By introducing approximate wave func- References Wof a Fermi gas by exciting an atom tions we connect the molecular produc- to a Rydberg state. Atoms of the back- tion rates of Rydberg molecules with [1] J. D. Whalen et al., arXiv:1903.11526 ground gas can form bound molecular different principal quantum numbers to (2019). states with the Rydberg atom via the scat- the corresponding correlation functions tering with its electron. These molecules evaluated at length scales of the associ- have a well-defined internuclear spacing. ated Rydberg radius.

52 Poster Session B Session

41 Single-photon distillation with a cavity QED system

Stephan Welte, S. Daiss, B. Hacker, L. Hartung, E. Distante, S. Ritter, L. Li, and G. Rempe Max Planck Institute of Quantum Optics, 85748 Garching, Germany

ustom-shaped single photons are an suppression of unwanted higher Fock References Cindispensable tool for many quan- components. Out of vacuum-dominated tum communication applications. We dis- light pulses, we distill single photons with [1] S. Daiss, S. Welte, B. Hacker, L. Li, G. till them out of incoming coherent optical fidelity of 66%. Applying our protocol to Rempe, PRL 122, 133603 (2019). pulses that are reflected from an atom- state-of-the-art fiber cavities would allow cavity system [1]. A suitable measurement to reach single-photon fidelities of up to on the atom is employed to herald the 96%.

Quantum gas microscopy of Rydberg macrodimers 42

Simon Hollerith, J. Zeiher, J. Rui, A. Rubio-Abadal, V. Walther, T. Pohl, D. M. Stamper-Kurn, I.Bloch, C. Groß Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

he sub-nanoscale size of typical di- of the lattice. By exciting pairs in the initial References Tatomic molecules hinders direct opti- two-dimensional atom array, we resolve cal access to their constituents. Rydberg more than 50 vibrational resonances. Us- [1] C. Boisseau, I. Simbotin, and R. Côté, macrodimers — bound states of two high- ing our spatially resolved detection, we Phys. Rev. Lett. 88, 133004 (2002). ly-excited Rydberg atoms [1,2,3] — feature observe the macrodimers by correlated interatomic distances easily exceeding atom loss and demonstrate control of [2] K. R. Overstreet, A. Schwettmann, J. optical wavelengths. Here we report the the molecular alignment by the choice of Tallant, D. Booth, and J. P. Shaffer, Nat. direct microscopic observation and de- the vibrational state. Our results allow for Phys. 5, 581 (2009). tailed characterization of such molecules rigorous testing of Rydberg interaction in a gas of ultracold atoms in an opti- potentials and highlight the potential of [3] H. Saßmannshausen and J. Deigl- cal lattice [4]. The bond length of about quantum gas microscopy for molecular mayr, Phys. Rev. Lett. 117, 083401 (2016). 0.7 µm, comparable to the size of small physics. bacteria, matches the diagonal distance [4] S. Hollerith et al., Science 364, 6441 (2019).

43 MBL to diffusive phase transition in the strongly coupled disordered t-V chain

G. De Tomasi, Daniel Hetterich, P. Sala, F. Pollmann Department of Physics, Technical University Munich, 85748 Garching, Germany

e study the disordered t-V chain the infinitely strong interaction term, we growth of bipartite entanglement entropy Win the limit of infinite interactions identify an MBL phase for sufficiently indicates that the delocalized part of the V. In this limit the Hamiltonian of interest strong but finite disorder values W > W_c phase diagram obeys diffusive transport describes constraint dynamics where a in the largest sector of the Hilbert space. properties. This is notable because most fermion is only allowed to hop left or right This can be understood by the fact that systems showing a MBL to delocalized if the total number of adjacent fermions in our model interactions effectively only transition behave subdiffusively in the ex- is unchanged. This divides the full Hilbert enter by additional constraints on the tended phase. space into unconnected blocks. Despite dynamics. Interestingly, for W < W_c, the

53 Poster Session Session B

In-plane anisotropy of the photon-helicity induced linear Hall effect in few-layer WTe 44 2

Jonas Kiemle1, P. Seifert1, F. Sigger1,2, K. Watanabe3, T. Taniguchi3, C. Kastl1,4, U. Wurstbauer1,2,5 and A. Holleitner1,2 1 Walter Schottky Institut, Technical University of Munich, Am Coulombwall 4, 85748 Garching, Germany 2 Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany 3 Advanced Materials Laboratory, Tsukuba, Ibaraki 305-0044, Japan 4 Molecular Foundry, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California, USA 5 Institute of Physics, WWU Muenster, Wilhelm-Klemm-Str. 10, Muenster, Germany

sing Hall photovoltage measure- orders of magnitude but is consistent References Uments, we demonstrate that a linear with the comparatively long spin lifetime transverse Hall voltage can be induced of carriers in the momentum-indirect [1] P. Seifert et al., Phys. Rev. B 99, in few-layer WTe2 under circularly polar- electron and hole pockets in WTe2. Our 161403(R) (2019). ized light illumination [1,2]. By applying a observation suggests that a helicity in- bias voltage along different crystal axes, duced non-equilibrium spin density on [2] P. Seifert et al., Nat. Comm. 9, 331 we find that the photon-helicity induced the Fermi surface after the initial charge (2018). Hall effect coincides with a particular crys- carrier relaxation gives rise to a linear Hall tal axis. Our results are consistent with the effect [1,4]. [3] P. Seifert et al., Nano Lett. B 99, 17, 2, underlying Berry curvature exhibiting a 973-979 (2017). dipolar distribution due to the breaking We acknowledge financial support by of crystal inversion symmetry. Using time the DFG via the German Excellence Strat- [4] P. Seifert et al., Phys. Rev. Lett. 122, resolved optoelectronic autocorrelation egy ‘Munich Center for Quantum Science 146804 (2019). spectroscopy [3], we find that the decay and Technology’ (MCQST) and project time of the detected Hall voltage exceeds HO3324/12. the electron-phonon scattering time by

Magnetic polarons and dynamical spin-charge separation under the microscope 45

Joannis Koepsell, J. Vijayan, P. Sompet, G. Salomon, S.Hirthe, T.A. Hilker, A. Bohrdt, F. Grusdt, E. Demler, I. Bloch, C. Gross Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA Department of Physics, Technical University of Munich, 85748 Garching, Germany Fakultät für Physik, Ludwig-Maximilians-Universität, 80799 München, Germany

he Fermi-Hubbard model offers an separation in one dimension [1] and the References Tintriguing playground to explore imaging of magnetic polarons in two di- strongly correlated many-body systems. mensions [2]. Due to our spin and charge [1] J. Vijayan, P. Sompet et al. (arX- Much of its complexity arises from the resolved imaging technique, our mea- iv:1905.13638). interplay of spin and charge degrees of surements are largely independent of freedom. We report on the experimental presumed models. Future extensions of [2] J. Koepsell et al. (Nature, in print, or study of one- and two-dimensional syn- these experiments may allow one to study arXiv:1811.06907). thetic Hubbard systems implemented on the interaction of polarons as a precursor the optical lattice platform. We discuss to collective many body physics in the our recent observations of spin-charge Hubbard model.

54 Poster Session B Session

Hybridized indirect excitons in MoS /WS heterobilayers 46 2 2

Florian Sigger1,2, J. Kiemle1, Fabian Kronowetter1, L. Sigl1,2, T. Sievers1, A. Holleitner1,2 and U. Wurstbauer1,2,3 1 Walter Schottky Institut, Technical University of Munich, Am Coulombwall 4, 85748 Garching, Germany 2 Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany 3 Institute of Physics, WWU Muenster, Wilhelm-Klemm-Str. 10, Muenster, Germany

nsembles of indirect or interlayer ex- valleys of the heterostructures [2]. We ob- References Ecitons (IXs) are intriguing systems to serve a field dependent level anti-cross- explore classical and quantum phases ing for the energetically lowest emission [1] Bastian Miller, Alexander Steinhoff, of interacting bosonic ensembles. IXs line, forming hybridized indirect excitons Borja Pano, Frank Jahnke, Alexander Hol- feature enlarged lifetimes due to the re- at low temperatures [2,3]. We discuss this leitner, Ursula Wurstbauer, Nano Lett., duced overlap of the electron-hole wave behavior in terms of a finite coupling of 17(9), 5229-5237 (2017). functions [1,2]. A field effect structure with the electronic states of the two TMDC few layer hexagonal boron nitrite (hBN) monolayers. Our results demonstrate the [2] Jonas Kiemle, Florian Sigger, Michael as insulator and few-layer graphene as design of novel nano-quantum materi- Lorke, Bastian Miller, Kenji Watanabe, gate-electrodes facilitates an electric field als prepared from artificial van der Waals Takashi Taniguchi, Alexander Holleitner, control of the IXs in a MoS2/WS2 hetero- solids with the possibility to in-situ control Ursula Wurstbauer, arXiv:1812.10697 bilayer [2]. A multiplet structure in the IX their physical properties via external stim- (2018). emission band can be observed even at uli such as electric fields. room temperature. Stark shift measure- [3] Shiyuan Gao, Li Yang, Catalin D. ments reveal the presence of a finite out- The work is supported by the Deutsche Spataru, Nano Lett., 17(12), 7809-7813, of plane dipole of the IXs. Due to a differ- Forschungsgemeinschaft (DFG) via ex- (2017). ent strength of the dipole and a distinct cellence clusters NIM and eConversion temperature dependence, we identify the as well as DFG projects WU 637/4-1 and IXs to stem from optical interband transi- HO3324/9-1. tions with electrons and holes in different

Quantum optoelectronics in materials with topological order 47 Christoph Kastl Walter Schottky Institut and Physics Department, Technical University of Munich, Am Coulombwall 4a, 85748 Garching

rystals with symmetry-protected to- scribed within the Shockley-Ramo theo- References Cpological order, such as topological rem [1]. In Weyl semimetals, instead, the insulators or Weyl semimetals, promise optoelectronic conductance is governed [1] P. Seifert, F. Sigger, J. Kiemle, K. Wata- coherent spin and charge transport even by non-zero Berry curvature, which results nabe, T. Taniguchi, C. Kastl, U. Wurst- in the presence of disorder at room tem- in an anomalous Hall-effect [2]. The non- bauer, A. Holleitner. Phys. Rev. Lett. 122, perature. Here, we explore light-matter equilibrium dynamics are dominated by 146804 (2019). interactions in topological materials, and coupling of spin and charge excitations we probe the interplay of non-trivial spin- and by ultrafast relaxation via the gapless [2] P. Seifert, M. Kundinger, G. Shi, X. He, momentum textures, optical excitation, surface states [3,4]. Our work elucidates K. Wu, Y. Li, A. Holleitner, C. Kastl. Phys. and non-equilibrium spin and charge car- fundamental properties of topological Rev. B 99, 161403 (2019). rier dynamics. We find an optoelectronic materials towards their integration in nov- quantum conductance e2/h of topologi- el quantum electronic circuits. [3] C. Kastl, C. Karnetzky, A. Brenneis, cal insulator surface states, which is de- F. Langrieger, A. Holleitner. IEEE J. Sel. Topics Quantum Electron. 23, 8700305 (2017).

[4] C. Kastl, C. Karnetzky, H. Karl., A. Hol- leitner. Nature Commun. 6, 6617 (2015).

55 Poster Session Session B

48 Interorbital interactions in Yb-171

Giulio Pasqualetti, O. Bettermann, N. Darkwah Oppong, L. Riegger, I. Bloch and S. Fölling Ludwig-Maximilians-Universität, Schellingstraße 4, 80799 München, Germany Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching, Germany Munich Center for Quantum Science and Technology (MCQST), Schellingstraße 4, 80799 München, Germany

tterbium is an alkaline-earth-like in state-dependent lattices has already References Yatom with a metastable clock state been observed [5]. In our experiment, in addition to the stable ground state. we investigate the interorbital scattering [1] A. V. Gorshkov et al. Nature Physics 6, In neutral ytterbium, state-dependent properties of ytterbium-171. Using clock- 289–295 (2010). lattices using these states can be em- line spectroscopy in a three-dimensional ployed for the realization of two-orbital optical lattice, we find an antiferromag- [2] M. Foss-Feig et al. Physical Review A magnetic Hamiltonians, including Kondo netic spin-exchange interaction and long 81 (2010). impurity and Kondo lattice models [1- lifetimes of the interacting states in the 3]. A fundamental parameter for Kondo lattice. Ytterbium-171 and ytterbium-173 [3] M. Foss-Feig et al. Physical Review A models is the spin-exchange interaction, should then make accessible quantum 82 (2010). which is known to be ferromagnetic for simulation of various and diverse re- ytterbium-173 [4], and whose dynamics gimes of Kondo-type models. [4] F. Scazza et al. Nature Physics 10, 779–784 (2014).

[5] L. Riegger et al. Physical Review Let- ters 120 (2018).

Bridging the THz gap: Toward ultrafast coherent on-chip electronics up to 10 THz 49

Fernandez Noelia1, Wörle M.3, Zimmermann P.1,2, Kienberger R.3,4, Holleitner A.1,2 1 Walter Schottky Institut and Physics Department, Technical University Munich, Am Coulombwall 4a, 85748 Garching, Germany 2 Nanosystems Initiative Munich (NIM), Schellingstrasse 4, 80799 Munich, Germany 3 Physik-Department E11, Technical University of Munich, James-Franck-Str. 1, 85748 Garching, Germany 4 Max-Planck-Institut für Quantenoptik, Hans Kopfermann-Straße 1, 85748 Garching, Germany

lassical electronics allows frequency with microscale lateral dimensions on var- References Ccomponents below hundreds of GHz ious substrates including sapphire, GaN, and photonics uses phenomena starting silica glass, and CVD-grown diamond. [1] D. Auston, IEEE J. Quantum Electron- at 10 THz with the so-called THz gap in We show how to include dielectric, ra- ics 19, 639–648 (1983). between, where components for signal diative and ohmic losses to describe the generation, conversion and detection pulse propagation in the striplines with [2] N. Fernandez et al., Ultrafast Phenom- remain difficult to implement. A promis- frequency components up to 10 THz [2]. ena and Nanophotonics XXIII, 109160R ing way to access this frequency range Our study gives a guideline to design co- (2019). is combining femtosecond optics and planar striplines compatible with on-chip on-chip electronics to generate electric time-resolved pump-probe spectroscopy [3] C. Karnetzky et al., Nature Communi- pulses in the THz domain. For information with sub-picosecond time resolution [3]. cations, 9(1), 2471 (2018). processing applications, it is essential to Consequently, we implement such on- guide such THz pulses in integrated on- chip spectroscopy scheme driven by the [4] P. Zimmermann et al. Nano Letters 19, chip circuits. We study a commonly used high peak electric fields provided by a 5 1172 (2019). implementation for on-chip signal trans- fs (FWHM) laser pulse with central wave- mission, so-called coplanar striplines, length 800 nm. We aim to further de- which in combination with photoconduc- crease the overall switching time and in- tive semiconductor (Auston) switches [1] crease the resolution of the time-resolved allow the generation and detection of THz measurements, for instance by plasmonic signals. We show the numerical computa- effects [4], and to exploit the carrier enve- tion of the effective refractive index and lope phase of the laser for controlling the attenuation of coplanar stripline circuits electronic response. 56 Poster Session B Session

50 Exploring mobility edges and many-body localization in a 1D quasiperiodic optical lattice

Thomas Kohlert1,2,3, S. Scherg1,2,3, X. Li4,5, H. Lüschen1,2, P. Bordia1,2, M. Schreiber1,2, S. Das Sarma4, I. Bloch1,2,3, and M. Aidelsburger1,2,3 1 Fakultät für Physik, Ludwig-Maximilians-Universität München, Schellingstr. 4, 80799 München, Germany 2 Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany 3 Munich Center for Quantum Science and Technology (MCQST), Schellingstr. 4, 80799 München, Germany 4 Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742-4111, USA 5 Department of Physics, City University of Hong-Kong, Kowloon, Hong Kong, China

single-particle mobility edge (SPME) mental evidence for the existence of an system exhibits many-body localization A marks a critical energy separating SPME in this system. Specifically, we find a (MBL) despite the presence of an SPME. extended from localized states. Certain regime where extended and localized sin- Moreover, we compare and contrast two one-dimensional systems with corre- gle-particle states coexist, in good agree- models with and without an SPME and lated disorder such as the generalized ment with theoretical simulations. experimentally and numerically explore Aubry-André (GAA) model are known to their dynamics on short and long times- have SPMEs in the corresponding single- In the corresponding interacting system cales. We discuss our results with respect particle spectrum. In this work, we realize we find that the dynamics is continuously to the potential existence of a many-body the GAA model with ultracold fermionic slowing down upon approaching a criti- intermediate phase. atoms in optical lattices. We find experi- cal disorder strength, indicating that the

Towards a suburban quantum network link 51

Robert Garthoff1, Wei Zhang1, T. van Leent1, K.Redeker1, M. Seubert1, D. Taray1, W. Rosenfeld1,2, and H. Weinfurter1,2 1 Fakultät für Physik, Ludwig-Maximilians-Universität, 80779 Munich, Germany 2 Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

uantum repeaters will allow scalable configuration [1,2]. Furthermore, to over- References Qquantum networks, which is essen- come losses during the frequency con- tial for large scale quantum communica- version and increase the event rate, we [1] M. Bock et al., Nat. Comm. 9, 1998 tion and distributed quantum computing. implemented a custom designed high- (2018). Yet, still missing on the road towards a NA microscope objective, increasing the quantum repeater, is to achieve entangle- photon collection efficiency by a factor of [2] R. Ikuta et al., Nat. Comm. 9, 1997 ment between quantum memories over 2.5. This now enabled the observation of (2018). long distances. Currently, we operate an atom-photon entanglement over a 10 km experimental setup which employs the optical fiber with a fidelity of 85%. [3] W. Rosenfeld et al., Phys. Rev. Lett. entanglement swapping protocol to gen- 119, 010402 (2017). erate heralded entanglement between Another crucial point is improving the two Rubidium 87 atoms separated by a coherence time of the atomic state. We [4] M. Körber et al., Nat. Photon. 12, 18- distance of 400 meters [1]. Here we represent a method using a standing-wave 21 (2018). port on results towards increasing this dis- dipole trap to suppress longitudinal field tance by at least an order of magnitude. components introduced by the strong fo- cussing and applying a coherent Raman Fiber based photonic quantum state dis- transfer to the entangled atomic state to tribution beyond a few kilometres makes make the atomic state combination 500 conversion to telecom wavelengths in- times less sensitive to magnetic-field fluc- dispensable. For this purpose, we use tuations [4]. We expect the atomic coher- quantum frequency conversion, where ence time to increase by two orders of the spontaneously emitted photon at 780 magnitude, which is sufficient for commu- nm is mixed with a strong pump field at nication over more than 100 km. 1600 nm inside a nonlinear waveguide crystal in a Sagnac-type interferometer

57 Poster Session Session B

52 Lattice-trapped lithium as tunable Floquet matter

C.J. Fujiwara, K. Singh, Z.A. Geiger, E.Q. Simmons, A. Cao, and David M. Weld University of California, Santa Barbara CA 93106, USA

egenerate lithium in modulated op- erties [1], direct imaging of Floquet-Bloch References Dtical lattices makes a near-ideal tes- bands using position-space Bloch oscilla- tbed for the experimental study of quan- tions [2], detailed experimental mapping [1] C.J. Fujiwara et al, Phys. Rev. Lett. 122, tum matter driven far from equilibrium. of the properties of prethermal Floquet 010402 (2019). We present a sequence of recent experi- matter [3], and an indication of anoma- mental results: flexible Floquet engineer- lously slow heating in a rapidly driven in- [2] Z.A. Geiger et al, Phys. Rev. Lett. 120, ing of band structure and transport prop- teracting gas. 213201 (2018).

[3] K. Singh et al, arXiv:1809.05554 (2018).

Site-selectively generated photon emitters in monolayer MoS via helium ion irradiation 2 53

J. Klein1,2 M. Lorke3,4, M. Florian3, F. Sigger1,2, Lukas Sigl1, S. Rey1, J. Wierzbowski1, K. Barthelmi1, A. Hötger1, J. Cerne5, K. Müller1, T. Taniguchi6, K. Watanabe6, U. Wurstbauer1,2, M. Kaniber1,2, M. Knap7, R. Schmidt8, J. J. Finley1,2, and A. W. Holleitner1,2 1 Walter Schottky Institut, Technical University of Munich, 85748 Garching, Germany 2 Nanosystems Initiative Munich (NIM), Schellingstr. 4, 80799 Munich, Germany 3 Institut für Theoretische Physik, Universität Bremen, P.O. Box 330 440, 28334 Bremen, Germany 4 Bremen Center for Computational Materials Science, 28359 Bremen, Germany 5 Department of Physics, The State University of New York, Buffalo, New York 14260, USA 6 National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan 7 Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany 8 Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

tomically thin TMDCs are well known The emitter line shape reveals a strong References Afor their strong light matter inter- asymmetry resembling the interaction action and exciton dominated spectral with LA/TA phonons. We attribute the [1] J. Klein et al., 2D Mater. 5, 1 (2017). response. Here, we demonstrate the de- emission to atomistic defects induced by terministic and site-selective generation the helium ion bombardment and discuss [2] J. Klein et al., arXiv:1901.01042v2 ac- of single defect emitters in a monolayer their origin in the light of ab-initio calcula- cepted (2019).

MoS2 van der Waals heterostructure by tions and scanning tunneling microscopy bombarding it with a nanometer-focused measurements. Finally, we demonstrate beam of helium ions. [1] Encapsulation the deterministic positioning of optically

of the defective MoS2 within hBN greatly active defects within the monolayer. enhances the optical quality and reveals narrow spectral lines with emission ener- We acknowledge financial support by the gies 100-220 meV below the neutral 2D DFG via the German Excellence Strategy exciton. [2] We spectroscopically investi- ‘Munich Center for Quantum Science and gate single emitters by performing pho- Technology’ (MCQST). toluminescence excitation spectroscopy.

58 Poster Session B Session

54 Trions in two-dimensional semiconductors - implications for exciton-polaron physics

Christian Fey, P. Schmelcher, A. Imamoglu and R. Schmidt Max-Planck-Instititut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748, Garching

e study the bound and excited be neglected in the low-energy exciton References Wstates of a system composed of charge carrier scattering. We discuss the three charge carriers in two-dimensional resulting implications for the observation [1] C. Fey, P. Schmelcher, A. Imamoglu, R. semiconductors. Our approach yields of exciton-Fermi polarons, a many-body Schmidt, in prep. accurate results for the binding energies system consisting of a single exciton inter- of excitons and trions in monolayers and acting with a Fermi sea of charge carriers [2] R. Schmidt, T. Enss, V. Pietilä, E. Dem- heterostructures of transition metal di- [2,3,4]. In particular, we find that effective ler, PRA 85, 021602 (2012). chalcogenides (TMD) [1]. Furthermore, it range corrections have a substantial ef- allows one to infer the scattering proper- fect on the optical absorption spectrum of [3] D. K. Efimkin and A. H. MacDonald, ties of excitons and electrons based on charge-doped TMDs, which have to be in- PRB 95, 035417 (2017). an exact solution of the three-body prob- cluded in an accurate description of Fer- lem. The predicted effective phase shift mi polaron formation in two-dimensional [4] M. Sidler, et al., Nature Physics 13, 255 implies that range corrections cannot semiconductors. (2017).

Emergent Glassy Dynamics in a Quantum Dimer Model 55 Johannes Feldmeier, F. Pollmann, M. Knap Department of Physics and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany

e consider the quench dynamics spatial correlations quickly relax to their References of a two-dimensional quantum di- thermal equilibrium. By contrast, the W [1] JF, F. Pollmann, M. Knap, mer model and determine the role of its staggered side of the first order transi- arXiv:1901.07597. kinematic constraints. We interpret the tion does not display thermalization on non-equilibrium dynamics in terms of the numerically accessible timescales. Based underlying equilibrium phase transitions on the model’s kinematic constraints, we consisting of a BKT-transition between uncover a mechanism of relaxation that a columnar ordered valence bond solid rests on emergent, highly detuned multi- (VBS) and a valence bond liquid (VBL), defect processes in a staggered back- as well as a first order transition between ground, which gives rise to slow, glassy a staggered VBS and the VBL. We find dynamics at low temperatures even in the that quenches from a columnar VBS are thermodynamic limit [1]. ergodic and both order parameters and

59 List of Participants Surname First Name Institute / University / Company Poster No.

Aidelsburger Monika LMU München Aladjidi Tangui Max Planck Institute of Quantum Optics Altshuler Boris Columbia University Back Christian TU Munich Baimuratov Anvar LMU München Bañuls Maria Carmen Max Planck Institute of Quantum Optics Barbone Matteo Walter Schottky Institute Barthelmi Katja Walter Schottky Institute Bender Julian Max Planck Institute of Quantum Optics Benelajla Meryem attocube systems AG 26 Bibo Julian TU Munich 22 Blatt Rainer Max Planck Institute of Quantum Optics Bloch Immanuel LMU München Bluhm Andreas TU Munich 9 Bohrdt Annabelle TU Munich 18 Bopp Frederik TU Munich 14 Borla Umberto TU Munich Brage Tomas Lund University Brandt Martin S. Walter Schottky Institute Brekenfeld Manuel Max Planck Institute of Quantum Optics Brosh Sella NVision Imaging Technologies GmbH Burger Florian Max Planck Institute of Quantum Optics Buser Maximilian LMU München Caro Matthias TU Munich Chen Lin TU Munich Christesen Joseph Max Planck Institute of Quantum Optics 15 Cuesta Javier TU Munich 17 Daiss Severin Max Planck Institute of Quantum Optics Dangel Christian Walter Schottky Institute 14 De Tomasi Giuseppe TU Munich 4 de Vega Ines LMU München Del Bimbo Gianni LMU München Deppe Frank Walther-Meißner-Institute Devra Amit TU Munich Diadamo Stephen TU Munich Duda Marcel Max Planck Institute of Quantum Optics 30 Duque Sierra Carolina Katholieke Universiteit Leuven Dürr Stephan Max Planck Institute of Quantum Optics Dziewior Jan LMU München 19 Eibensteiner Klaus kiutra GmbH Emonts Patrick Max Planck Institute of Quantum Optics Erdmenger Johanna Julius-Maximilians-Universität Würzburg Fedorov Kirill Walther-Meißner-Institute 11 Feldmeier Johannes TU Munich 55 Fernandez Noelia Walter Schottky Institute 49 Fey Christian Max Planck Institute of Quantum Optics 54 Finley Jonathan Walter Schottky Institute Freiwang Peter LMU München 21 Garthoff Robert LMU München 51 Glaser Steffen TU Munich 60 List of Participants Surname First Name Institute / University / Company Poster No.

Goeser Jonas LMU München Gonzalez-Tudela Alejandro Autonomous University of Madrid Govindaraj Rengaraj LMU München Gritsch Andreas Max Planck Institute of Quantum Optics Gross Rudolf Walther-Meißner-Institute Grusdt Fabian TU Munich 20 Gschwendtner Martina TU Munich 10 Haenggli Lisa TU Munich Hagymasi Imre LMU München Haindl Rudolf Max Planck Institute of Quantum Optics Hartmann Michael University of Erlangen-Nürnberg Hartung Lukas Max Planck Institute of Quantum Optics Hasenöhrl Markus TU Munich Haslbeck Franz TU Munich Hémery Kévin TU Munich 5 Hetterich Daniel TU Munich 43 Hoch David TU Munich 27 Högele Alexander LMU München Hoffmann Markus Google Holleitner Alexander TU Munich Hollerith Simon Max Planck Institute of Quantum Optics 42 Hötger Alexander Walter Schottky Institute Hübl Hans Walther-Meißner-Institute Ianzano Christopher Max Planck Institute of Quantum Optics Impertro Alexander LMU München Irber Dominik Walter Schottky Institute 7 Jansen Sabine LMU München Janßen Gisbert TU Munich 23 Jelezko Fedor Ulm University Jia Yifan TU Munich Kastenmüler Simon SNS Kastl Christoph Walter Schottky Institute 47 Kiemle Jonas Walter Schottky Institute 44 Kilber Natalie Microsoft Germany GmbH Klein Julian Walter Schottky Institute Kliesch Alexander TU Munich Knap Michael TU Munich Knips Lukas LMU München Koepsell Joannis Max Planck Institute of Quantum Optics 45 Kohlert Thomas Max Planck Institute of Quantum Optics 50 König Robert TU Munich Kremser Malte Walter Schottky Institute Kronowetter Fabian Walter Schottky Institute Kuhlenkamp Clemens TU Munich 24 Kurecic Ivana Max Planck Institute of Quantum Optics Langenfeld Stefan Max Planck Institute of Quantum Optics Lin Sheng-Hsuan TU Munich Lovas Izabella TU Munich 16 Mader Matthias LMU München 61 List of Participants Surname First Name Institute / University / Company Poster No.

Marx Achim Walther-Meißner-Institute Meinecke Jasmin Max Planck Institute of Quantum Optics Merkel Benjamin Max Planck Institute of Quantum Optics 6 Morin Olivier Max Planck Institute of Quantum Optics Moser David LMU München Müller Kai TU Munich Nguyen Dinh Thi LMU München Nicotina Amanda TU Munich Nötzel Janis TU Munich Oberhauser Moritz TU Munich Otgonbaatar Soronzonbold German-Mongolian Institute for Resources and Technology Palm Felix LMU München Partanen Matti Walther-Meißner-Institute Pasqualetti Giulio LMU München 48 Petrić Marko Walter Schottky Institute 12 Pogorzalek Stefan Walther-Meißner-Insitute Pollmann Frank TU Munich Poot Menno TU Munich Preciado Garcia Sthefani TU Munich Punk Matthias LMU München Regnat Alexander kiutra GmbH Reinhard Friedemann TU Munich Reiserer Andreas Max Planck Institute of Quantum Optics Rempe Gerhard Max Planck Institute of Quantum Optics Renger Michael Walther-Meißner-Insitute 28 Repp Daniel TU Munich Rey Sergio Walter Schottky Institute Rojas Hector Jonathan Walter Schottky Institute Roy Ananda TU Munich 32 Rui Jun Max Planck Institute of Quantum Optics Sabonis David University of Copenhagen Sala Pablo TU Munich 37 Schlotthauer Heinrich Schmauder Christian Max Planck Institute of Quantum Optics Schollwöck Ulrich LMU München Schuch Norbert Max Planck Institute of Quantum Optics Schuckert Alexander TU Munich 3 Schulte-Herbrüggen Thomas TU Munich 31 Schulz Tomek kiutra GmbH 34 Schwartz Ilai NVision Imaging Technologies GmbH Schweizer Christian LMU München 35 Schwienbacher Daniel Walther-Meißner-Institute 1 Seiler Anna LMU München Seltmann Martin TU Munich 36 Seubert Matthias LMU München Sievers Tammo Walter Schottky Institute Sigger Florian Walter Schottky Institute 46 Sigl Lukas Walter Schottky Institute 53 Smith Adam TU Munich 8 62 List of Participants Surname First Name Institute / University / Company Poster No.

Solodovnik Alexander TU Munich Sompet Pimonpan Max Planck Institute of Quantum Optics Spallek Jan kiutra GmbH Sperzel Marc kiutra GmbH Stäbler Florian LMU München Stamper-Kurn Dan University of California - Berkeley Stanchev Boris LMU München Staub Etienne Max Planck Institute of Quantum Optics Stenzel Leo LMU München Strohauer Stefan TU Munich Swaminathan Koushik LMU München Taray Derya LMU München Terrasanta Giulio EPFL Thomas Philip Max Planck Institute of Quantum Optics Thönniß Julian LMU München Tolazzi Nicolas Max Planck Institute of Quantum Optics Tornow Sabine Munich University of Applied Sciences Trautmann Jan Max Planck Institute of Quantum Optics 38 Udem Thomas Max Planck Institute of Quantum Optics Vadia Samarth LMU München 33 van Leent Tim LMU München Villoresi Paolo University of Padova Vilsmeier Franz TU Munich Vogl David Walter Schottky Institute 13 vom Ende Frederik TU Munich 39 von Grafenstein Katinka LMU München von Milczewski Jonas Max Planck Institute of Quantum Optics Wagner Marcel Max Planck Institute of Quantum Optics 40 Warzel Simone TU Munich Wehner Stephanie TU Delft Wei David Max Planck Institute of Quantum Optics Wei Zhi-Yuan Max Planck Institute of Quantum Optics Weichselbaumer Stefan Walther-Meissner-Institute 2 Weigel Walter Huawei Weinbrenner Paul Walter Schottky Institute 29 Weinfurter Harald LMU München Weiss Lorenz Max Planck Institute of Quantum Optics 25 Weitz Thomas LMU München Weld David University of California - Santa Barbara 52 Welte Stephan Max Planck Institute of Quantum Optics 41 Wienand Julian LMU München Winterer Felix LMU München Wintersperger Karen LMU München Wolf Michael TU Munich Yang Yilun Max Planck Institute of Quantum Optics Zerhoch Jonathan Walter Schottky Institute 13 Zhang Wei LMU München 51 Zhao Shen LMU München Zhou Saibin Max Planck Institute of Quantum Optics 63 Munich Conference on Quantum Science & Technology Time Monday, 8 July Tuesday, 9 July 9:00 Boris Altshuler (p.08) Fedor Jelezko (p.21) Quantum Many-Body Systems between Quantum sensing enabled by diamond Localization and Ergodicity

9:45 Alexander W. Holleitner (p.09) Friedemann Reinhard (p.22) Atomistic defect states as quantum emitters in Quantum sensors for microwave radiation

monolayer MoS2

10:10 Matthias Punk (p.10) Thomas Udem (p.23) Charge density wave quantum criticality in two Challenging QED with atomic hydrogen dimensional metals

10:35 Coffee Break Coffee Break

11:00 Dan M. Stamper-Kurn (p.11) Johanna Erdmenger (p.24) Magnetism and frustration in quantum gases New insights into quantum information from black holes

11:45 Michael Knap (p.12) Alejandro González-Tudela (p.25) New routes to probe the two-dimensional Fermi- Analog Quantum Chemistry Simulation with Cold Atoms Hubbard model

12:10 Monika Aidelsburger (p.13) Mari Carmen Bañuls (p.26) Synthetic gauge fields with ultracold atoms in Using tensor network states for lattice gauge theories periodically-driven lattices

12:35 Lunch Lunch

13:30 Poster Session A Poster Session B

14:30 Rainer Blatt (p.14) Tomas Brage (p.27) Quantum computation and quantum simulation with What does Gender have to do with Physics? strings of trapped Ca+ ions

15:15 Frank Deppe (p.15) Panel Discussion (p.28) Quantum microwaves: Secure communication, cryo- Challenges in quantum science and technologies genic LAN cables, and illumination from basic research to applications

15:40 Michael J. Hartmann (p.16) with guests from industry Neural-network approach to dissipative quantum many-body dynamics

16:05 Coffee Break Coffee Break

16:30 Stephanie Wehner (p.17) Paolo Villoresi (p.29) tba Quantum Communications in Space: new opportunities for basic science and applications

17:15 Robert König (p.18) Andreas Reiserer (p.30) Quantum advantage with noisy shallow circuits in 3D Towards quantum networks with Erbium dopants

17:40 Sabine Jansen (p.19) Olivier Morin (p.31) From quantum mechanics to probability theory - Qubit memories for quantum networks and back?

18:15 Bus departures at Deutsches Museum Research Unit A - Quantum Information Theory - 18:50 Research Unit B - Quantum Simulation

19:00 Arrival at Microsoft Atrium München Research Unit C - Quantum Computing Research Unit D - Quantum Communication 19:30 Science Slam (p.20) - Research Unit E - Quantum Metrology and Sensing 21:30 Research Unit F - Quantum Matter Research Unit G - Explorative Research Special Sessions