1 QSIT Newsletter [Type text] Newsletter QSIT Newsletter July 2015 1. Scientific News Nicolas Brunner’s group, Geneva Disproving the Peres conjecture by showing Bell nonlocality from bound entanglement: In 1999, Bell$Nonlocality$ Non-positive$ Asher Peres conjectured that the weakest form Partial$Transpose$$ of entanglement (so-called bound entanglement) ?" can never result in the strongest manifestation of the phenomenon, namely Bell nonlocality. Here this conjecture is proven to be false, thus solving a ?" famous open problem in quantum information theory. This clarifies the relation between three Entanglement$ fundamental aspects of entanglement. Distillability$ - Tamás Vértesi, Nicolas Brunner, Nature Commu- nications 5, 5297 (2015): http://www.nature.com/ncomms/2014/141105/n comms6297/full/ncomms6297.html Klaus Ensslin’s, Thomas Ihn’s, and Werner Wegscheider’s group, Zurich: Non-equilibrium transport in density modulated might indicate a more complex structure of the phases of the second Landau level: Nonequi- bubble phases than currently anticipated, or a librium transport in the reentrant integer quantum breaking of the particle-hole symmetry. Such a Hall phases of the second Landau level has been symmetry breaking in the second Landau level investigated. At high currents, a transition from the might also have consequences for the physics at reentrant integer quantum Hall phases to classical filling factor 5/2. Hall conduction is observed. Surprisingly, this - S. Baer, C. Rössler, S. Hennel, H.C. Overweg, T. Ihn, transition is markedly different for the hole- and K. Ensslin, C. Reichl, and W. Wegscheider, Phys. Rev. electron sides of each spin branch. While the hole B 91, 195414 (2015): bubble phases exhibit a sharp transition to an http://journals.aps.org/prb/abstract/10.1103/Phy isotropic compressible phase, the transition for the sRevB.91.195414 electron side occurs via an intermediate phase. This Klaus Ensslin’s, Thomas Ihn’s, and Werner Wegscheider’s group, Zurich, & Daniel Loss’ group, Basel: Characterization of spin-orbit interactions of The spin-orbit components, being of great GaAs heavy holes using a quantum point importance for quantum computing applications, contact: Transport experiments have been are characterized in terms of magnitude and spin performed in high-quality quantum point contacts structure. In light of these results, the level- embedded in a GaAs two-dimensional hole gas. The dependent effective g factor in an in-plane field can strong spin-orbit interaction results in peculiar be explained. Through a tilted magnetic field transport phenomena, including the previously analysis, it has been shown that the quantum point observed anisotropic Zeeman splitting and level- contact out-of- plane g factor saturates around the dependent effective g factors. Here additional predicted 7.2 bulk value. effects are found, namely, the crossing and the anticrossing of spin-split levels depending on - F. Nichele, S. Chesi, S. Hennel, A. Wittmann, C. Gerl, subband index and magnetic field direction. The W. Wegscheider, D. Loss, T. Ihn, and K. Ensslin, Phys. experimental observations are reconciled in a Rev. Lett. 113, 046801 (2014): heavy-hole effective spin-orbit Hamiltonian where http://journals.aps.org/prl/abstract/10.1103/Phys cubic- and quadratic-in-momentum terms appear. RevLett.113.046801 2 QSIT Newsletter [Type text] QSIT Newsletter Tilman Esslinger’s group, Zurich Observation of quantized conductance in Experimental realization of the topological neutral matter: In experiments using ultracold Haldane model with ultracold fermions Tilman atoms and laser light, researchers from Tilman Esslinger and collaborators have implemented in Esslinger's group have measured a stepwise change their experimental setup an idea for a new class of in conductivity as the atoms pass through tiny materials first proposed by the British physicist structures. This is the first time that this quantum Duncan Haldane in 1988. In these systems, a effect has been observed for electrically neutral quantized Hall effect appears despite the absence of particles. a magnetic field. The key step for the realization was to place ultracold potassium atoms into a honeycomb lattice created by laser beams and shaken periodically on a circular trajectory. Fig.: A point contact through which neutral, ultracold Fig.: A Möbius strip can't be transformed into a normal strip without cutting atoms flow. - Sebastian Krinner, David Stadler, Dominik - Gregor Jotzu, Michael Messer, Rémi Desbuquois, Husmann, Jean-Philippe Brantut, and Tilman Martin Lebrat, Thomas Uehlinger, Daniel Greif & Esslinger, Nature, 517, 64, (2015) Tilman Esslinger, Nature 515, 237 (2014) http://www.nature.com/nature/journal/v517/n75 http://www.nature.com/nature/journal/v515/n75 32/full/nature14049.html 26/full/nature13915.html - In the media: ETH News - In the media: ETH News Jonathan Home’s group, Zurich Spin–motion entanglement and state diagnosis Quantum harmonic oscillator state synthesis by with squeezed oscillator wavepackets: reservoir engineering: Jonathan Home and his Researchers of this group have revealed the strange group have demonstrated new methods for nature of quantum physics in experiments on a engineering quantum states of a trapped-ion trapped calcium ion. By cooling down the state of mechanical oscillator based on dissipative pumping, the trapped ion they were able to create a so-called where the desired superposition state is produced 'squeezed Schrödinger cat' state. This achievement as the steady state of the pumping. The key element might open the way to new technologies. in this work was the introduction of novel spin- - Hsiang-Yu Lo, Daniel Kienzler, Ludwig de Clercq,, motion couplings which allow control of the Matteo Marinelli, Vlad Negnevitsky Ben C. Keitch & oscillator in a rotated eigenstate basis. Jonathan P. Home, Nature 521, 336–339 (2015) - D. Kienzler*, H.-Y. Lo, B. Keitch, L. de Clercq, F. http://www.nature.com/nature/journal/v521/n75 Leupold, F. Lindenfelser, M. Marinelli, V. 52/full/nature14458.html Negnevitsky, J. P. Home*Science Vol. 347 no. 6217 - Nature - News and Views 521, 295–296 (2015) pp. 53-56 (2015) http://www.nature.com/nature/journal/v521/n75 http://www.sciencemag.org/content/347/6217/5 52/full/521295a.html 3.abstract - In the media: ETH News, Spektrum der Wissenschaft, NZZ online . Sebastian Huber’s group, Zurich Observation of helical edge states in a rise to a new design principle for acoustic meta- mechanical topological insulator: In an materials with applications in vibration isolation experiment with an array of 270 coupled pendula, and sound guiding. Roman Süsstrunk and Sebastian Huber could - Roman Süsstrunk, Sebastian D. Huber, Science 349, establish a link between quantum mechanical 47 (2015) topological states of electrons and the world of http://www.sciencemag.org/content/349/6243/47 mechanical oscillators. Their findings might give - In the media: ETH News, phys.org 3 QSIT Newsletter [Type text] QSIT Newsletter Atac Imamoglu’s group, Zurich Cavity quantum electrodynamics with many- - S. Smolka, W. Wuester, F. Haupt, S. Faelt, W. body states of a two-dimensional electron gas: Wegscheider, A. Imamoglu, Science 346 (6207) 332 Light-matter interaction has played a central role in (2014) understanding as well as engineering new states of http://www.sciencemag.org/content/346/6207/3 matter. Reversible coupling of excitons and photons 32 enabled groundbreaking results in condensation - In the media: ETH News and superfluidity of nonequilibrium quasiparticles with a photonic component. We investigated such cavity-polaritons in the presence of a high-mobility two-dimensional electron gas, exhibiting strongly correlated phases. When the cavity was on resonance with the Fermi level, we observed previously unknown many-body physics associated with a dynamical hole-scattering potential. In finite magnetic fields, polaritons show distinct signatures of integer and fractional quantum Hall ground states. Our results lay the groundwork for probing Fig.: Three-dimensional representation of the nonequilibrium dynamics of quantum Hall states polariton states of a two-dimensional electron gas in and exploiting the electron density dependence of presence of a high magnetic field. polariton splitting so as to obtain ultrastrong optical nonlinearities. Patrick Maletinsky’s group, Basel Strong mechanical driving of a single electron objects that’s offered by crystal-strain upon bending spin: In this work, we demonstrated the coherent of the cantilever. The driving mechanic is strong and driving of a single electronic spin by purely robust and allowed us to demonstrate a significant mechanical means. We achieved this driving by protection of the spin from decoherence - a central embedding the spin (in form of a Nitrogen-Vacancy asset for possible future applications of this device center in diamond) in a diamond cantilever and by in quantum technologies. exploiting the intrinsic coupling between these two - Just accepted in Nature Physics Patrick Maletinsky’s and Daniel Loss’ group, Basel High-efficiency resonant amplification of weak available, our proposed set-up is sensitive enough magnetic fields for single spin magnetometry at to detect a single nuclear spin within ten room temperature: Magnetic resonance milliseconds of data acquisition at room techniques not only provide powerful imaging tools temperature. The sensitivity is practically that have revolutionized medicine, but they have a unchanged when the ferromagnet surface