A Scanning Transmon Qubit for Strong Coupling Circuit Quantum Electrodynamics
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Engineering the Coupling of Superconducting Qubits
Engineering the coupling of superconducting qubits Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der RWTH Aachen University zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften genehmigte Dissertation vorgelegt von M. Sc. Alessandro Ciani aus Penne, Italien Berichter: Prof. Dr. David DiVincenzo Prof. Dr. Fabian Hassler Tag der mündlichen Prüfung: 12 April 2019 Diese Dissertation ist auf den Internetseiten der Universitätsbibliothek verfügbar. ii «Considerate la vostra semenza: fatti non foste a viver come bruti, ma per seguir virtute e conoscenza.» Dante Alighieri, "La Divina Commedia", Inferno, Canto XXVI, vv. 118-120. iii Abstract The way to build a scalable and reliable quantum computer that truly exploits the quantum power faces several challenges. Among the various proposals for building a quantum computer, superconducting qubits have rapidly progressed and hold good promises in the near-term future. In particular, the possibility to design the required interactions is one of the most appealing features of this kind of architecture. This thesis deals with some detailed aspects of this problem focusing on architectures based on superconducting transmon-like qubits. After reviewing the basic tools needed for the study of superconducting circuits and the main kinds of superconducting qubits, we move to the analyisis of a possible scheme for realizing direct parity measurement. Parity measurements, or in general stabilizer measurements, are fundamental tools for realizing quantum error correct- ing codes, that are believed to be fundamental for dealing with the problem of de- coherence that affects any physical implementation of a quantum computer. While these measurements are usually done indirectly with the help of ancilla qubits, the scheme that we analyze performs the measurement directly, and requires the engi- neering of a precise matching condition. -
Simulating Quantum Field Theory with a Quantum Computer
Simulating quantum field theory with a quantum computer John Preskill Lattice 2018 28 July 2018 This talk has two parts (1) Near-term prospects for quantum computing. (2) Opportunities in quantum simulation of quantum field theory. Exascale digital computers will advance our knowledge of QCD, but some challenges will remain, especially concerning real-time evolution and properties of nuclear matter and quark-gluon plasma at nonzero temperature and chemical potential. Digital computers may never be able to address these (and other) problems; quantum computers will solve them eventually, though I’m not sure when. The physics payoff may still be far away, but today’s research can hasten the arrival of a new era in which quantum simulation fuels progress in fundamental physics. Frontiers of Physics short distance long distance complexity Higgs boson Large scale structure “More is different” Neutrino masses Cosmic microwave Many-body entanglement background Supersymmetry Phases of quantum Dark matter matter Quantum gravity Dark energy Quantum computing String theory Gravitational waves Quantum spacetime particle collision molecular chemistry entangled electrons A quantum computer can simulate efficiently any physical process that occurs in Nature. (Maybe. We don’t actually know for sure.) superconductor black hole early universe Two fundamental ideas (1) Quantum complexity Why we think quantum computing is powerful. (2) Quantum error correction Why we think quantum computing is scalable. A complete description of a typical quantum state of just 300 qubits requires more bits than the number of atoms in the visible universe. Why we think quantum computing is powerful We know examples of problems that can be solved efficiently by a quantum computer, where we believe the problems are hard for classical computers. -
Direct Dispersive Monitoring of Charge Parity in Offset-Charge
PHYSICAL REVIEW APPLIED 12, 014052 (2019) Direct Dispersive Monitoring of Charge Parity in Offset-Charge-Sensitive Transmons K. Serniak,* S. Diamond, M. Hays, V. Fatemi, S. Shankar, L. Frunzio, R.J. Schoelkopf, and M.H. Devoret† Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA (Received 29 March 2019; revised manuscript received 20 June 2019; published 26 July 2019) A striking characteristic of superconducting circuits is that their eigenspectra and intermode coupling strengths are well predicted by simple Hamiltonians representing combinations of quantum-circuit ele- ments. Of particular interest is the Cooper-pair-box Hamiltonian used to describe the eigenspectra of transmon qubits, which can depend strongly on the offset-charge difference across the Josephson element. Notably, this offset-charge dependence can also be observed in the dispersive coupling between an ancil- lary readout mode and a transmon fabricated in the offset-charge-sensitive (OCS) regime. We utilize this effect to achieve direct high-fidelity dispersive readout of the joint plasmon and charge-parity state of an OCS transmon, which enables efficient detection of charge fluctuations and nonequilibrium-quasiparticle dynamics. Specifically, we show that additional high-frequency filtering can extend the charge-parity life- time of our device by 2 orders of magnitude, resulting in a significantly improved energy relaxation time T1 ∼ 200 μs. DOI: 10.1103/PhysRevApplied.12.014052 I. INTRODUCTION charge states, like a usual transmon but with measurable offset-charge dispersion of the transition frequencies The basic building blocks of quantum circuits—e.g., between eigenstates, like a Cooper-pair box. This defines capacitors, inductors, and nonlinear elements such as what we refer to as the offset-charge-sensitive (OCS) Josephson junctions [1] and electromechanical trans- transmon regime. -
Probing an Ultracold-Atom Crystal with Matter Waves
Probing an Ultracold-Atom Crystal with Matter Waves Bryce Gadway, Daniel Pertot, Jeremy Reeves, and Dominik Schneble Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA (Dated: October 27, 2018) Abstract Atomic quantum gases in optical lattices serve as a versatile testbed for important concepts of modern condensed-matter physics. The availability of methods to charac- terize strongly correlated phases is crucial for the study of these systems. Diffraction techniques to reveal long-range spatial structure, which may complement in situ de- tection methods, have been largely unexplored. Here we experimentally demonstrate that Bragg diffraction of neutral atoms can be used for this purpose. Using a one- dimensional Bose gas as a source of matter waves, we are able to infer the spatial ordering and on-site localization of atoms confined to an optical lattice. We also study the suppression of inelastic scattering between incident matter waves and the lattice-trapped atoms, occurring for increased lattice depth. Furthermore, we use atomic de Broglie waves to detect forced antiferromagnetic ordering in an atomic spin mixture, demonstrating the suitability of our method for the non-destructive detection of spin-ordered phases in strongly correlated atomic gases. arXiv:1104.2564v2 [cond-mat.quant-gas] 20 Feb 2012 1 The diffraction of electron and neutron matter waves from crystalline structures is a stan- dard tool in crystallography, complementing x-ray techniques [1]. The advent of quantum gases in optical lattices has introduced a new class of highly controllable systems that mimic the physics of solids at lattice constants that are three orders of magnitude larger [2], and it appears natural to ask about a possible role for atomic matter-wave diffraction in the characterization of these systems [3, 4]. -
Simulating Quantum Field Theory with a Quantum Computer
Simulating quantum field theory with a quantum computer John Preskill Bethe Lecture, Cornell 12 April 2019 Frontiers of Physics short distance long distance complexity Higgs boson Large scale structure “More is different” Neutrino masses Cosmic microwave Many-body entanglement background Supersymmetry Phases of quantum Dark matter matter Quantum gravity Dark energy Quantum computing String theory Gravitational waves Quantum spacetime particle collision molecular chemistry entangled electrons A quantum computer can simulate efficiently any physical process that occurs in Nature. (Maybe. We don’t actually know for sure.) superconductor black hole early universe Opportunities in quantum simulation of quantum field theory Exascale digital computers will advance our knowledge of QCD, but some challenges will remain, especially concerning real-time evolution and properties of nuclear matter and quark-gluon plasma at nonzero temperature and chemical potential. Digital computers may never be able to address these (and other) problems; quantum computers will solve them eventually, though I’m not sure when. The physics payoff may still be far away, but today’s research can hasten the arrival of a new era in which quantum simulation fuels progress in fundamental physics. Collaborators: Stephen Jordan, Keith Lee, Hari Krovi arXiv: 1111.3633, 1112.4833, 1404.7115, 1703.00454, 1811.10085 Work in progress: Alex Buser, Junyu Liu, Burak Sahinoglu ??? Quantum Supremacy! Quantum computing in the NISQ Era The (noisy) 50-100 qubit quantum computer is coming soon. (NISQ = noisy intermediate-scale quantum .) NISQ devices cannot be simulated by brute force using the most powerful currently existing supercomputers. Noise limits the computational power of NISQ-era technology. -
Redefining Metrics in Near-Term Devices for Quantum Information
Mo01 Redefining metrics in near-term devices for quantum information processing Antonio C´orcoles IBM E-mail: [email protected] The outstanding progress in experimental quantum computing over the last couple of decades has pushed multi-qubit gate error rates in some platforms well below 1%. How- ever, as the systems have grown in size and complexity so has the richness of the inter- actions within them, making the meaning of gate fidelity fade when taken isolated from its environment. In this talk I will discuss this topic and offer alternatives to benchmark the performance of small quantum processors for near-term applications. Mo02 Efficient simulation of quantum error correction under coherent error based on non-unitary free-fermionic formalism Yasunari Suzuki1,2, Keisuke Fujii3,4, and Masato Koashi1,2 1Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan 2Photon Science Center, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan 3 Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan 4JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan In order to realize fault-tolerant quantum computation, tight evaluation of error threshold under practical noise models is essential. While non-Clifford noise is ubiquitous in experiments, the error threshold under non-Clifford noise cannot be efficiently treated with known approaches. We construct an efficient scheme for estimating the error threshold of one-dimensional quantum repetition code under non-Clifford noise[1]. -
Quantum Simulation Using Photons
Quantum Simulation Using Photons Philip Walther Faculty of Physics Enrico Fermi Summer School University of Vienna Varenna, Italy Austria 24-25 July 2016 Lecture I: Quantum Photonics Experimental Groups doing Quantum Computation & Simulation QuantumComputing@UniWien . Atoms (Harvard, MIT, MPQ, Hamburg,…) : single atoms in optical lattices transition superfluid → Mott insulator . Trapped Ions (Innsbruck, NIST, JQI Maryland, Ulm…): quantum magnets Dirac’s Zitterbewegung frustrated spin systems open quantum systems . NMR (Rio, SaoPaulo, Waterloo, MIT, Hefei,…): simulation of quantum dynamics ground state simulation of few (2-3) qubits . Superconducting Circuits (ETH, Yale, Santa Barbara,…): phase qudits for measuring Berry phase gate operations . Single Photons (Queensland, Rome, Bristol, Vienna,…) simulation of H2 potential (Nat.Chem 2, 106 (2009)) quantum random walks (PRL 104, 153602 (2010)) spin frustration Architecture race for quantum computers QuantumComputing@UniWien • UK: 270 M₤ • Netherlands: 135 M€ Why Photons ? QuantumComputing@UniWien . only weak interaction with environment (good coherence) . high-speed (c), low-loss transmission (‘flying qubits”) . good single-qubit control with standard optical components (waveplates, beamsplitters, mirrors,…) . feasible hardware requirements (no vaccuum etc.) . disadvantage: weak two-photon interactions (requires non-linear medium -> two-qubit gates are hard) Outlook of the Course QuantumComputing@UniWien (1) Quantum Photonics Concepts and Technology (2) Quantum Simulation (3) Photonic Quantum Simulation Examples . Analog Quantum Simulator . Digital Quantum Simulator . Intermediate Quantum Computation (4) Schemes based on superposition of gate orders Basic Elements in Photonic Quantum Computing and Quantum Simulation Literature Suggestion QuantumComputing@UniWien (1) Five Lectures on Optical Quantum Computing (P. Kok) http://arxiv.org/abs/0705.4193v1 (2007) (2) Linear optical quantum computing with photonic qubits Rev. -
Higher Levels of the Transmon Qubit
Higher Levels of the Transmon Qubit MASSACHUSETTS INSTITUTE OF TECHNirLOGY by AUG 15 2014 Samuel James Bader LIBRARIES Submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Bachelor of Science in Physics at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2014 @ Samuel James Bader, MMXIV. All rights reserved. The author hereby grants to MIT permission to reproduce and to distribute publicly paper and electronic copies of this thesis document in whole or in part in any medium now known or hereafter created. Signature redacted Author........ .. ----.-....-....-....-....-.....-....-......... Department of Physics Signature redacted May 9, 201 I Certified by ... Terr P rlla(nd Professor of Electrical Engineering Signature redacted Thesis Supervisor Certified by ..... ..................... Simon Gustavsson Research Scientist Signature redacted Thesis Co-Supervisor Accepted by..... Professor Nergis Mavalvala Senior Thesis Coordinator, Department of Physics Higher Levels of the Transmon Qubit by Samuel James Bader Submitted to the Department of Physics on May 9, 2014, in partial fulfillment of the requirements for the degree of Bachelor of Science in Physics Abstract This thesis discusses recent experimental work in measuring the properties of higher levels in transmon qubit systems. The first part includes a thorough overview of transmon devices, explaining the principles of the device design, the transmon Hamiltonian, and general Cir- cuit Quantum Electrodynamics concepts and methodology. The second part discusses the experimental setup and methods employed in measuring the higher levels of these systems, and the details of the simulation used to explain and predict the properties of these levels. Thesis Supervisor: Terry P. Orlando Title: Professor of Electrical Engineering Thesis Supervisor: Simon Gustavsson Title: Research Scientist 3 4 Acknowledgments I would like to express my deepest gratitude to Dr. -
Magnetically Induced Transparency of a Quantum Metamaterial Composed of Twin flux Qubits
ARTICLE DOI: 10.1038/s41467-017-02608-8 OPEN Magnetically induced transparency of a quantum metamaterial composed of twin flux qubits K.V. Shulga 1,2,3,E.Il’ichev4, M.V. Fistul 2,5, I.S. Besedin2, S. Butz1, O.V. Astafiev2,3,6, U. Hübner 4 & A.V. Ustinov1,2 Quantum theory is expected to govern the electromagnetic properties of a quantum metamaterial, an artificially fabricated medium composed of many quantum objects acting as 1234567890():,; artificial atoms. Propagation of electromagnetic waves through such a medium is accompanied by excitations of intrinsic quantum transitions within individual meta-atoms and modes corresponding to the interactions between them. Here we demonstrate an experiment in which an array of double-loop type superconducting flux qubits is embedded into a microwave transmission line. We observe that in a broad frequency range the transmission coefficient through the metamaterial periodically depends on externally applied magnetic field. Field-controlled switching of the ground state of the meta-atoms induces a large suppression of the transmission. Moreover, the excitation of meta-atoms in the array leads to a large resonant enhancement of the transmission. We anticipate possible applications of the observed frequency-tunable transparency in superconducting quantum networks. 1 Physikalisches Institut, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany. 2 Russian Quantum Center, National University of Science and Technology MISIS, Moscow, 119049, Russia. 3 Moscow Institute of Physics and Technology, Dolgoprudny, 141700 Moscow region, Russia. 4 Leibniz Institute of Photonic Technology, PO Box 100239, D-07702 Jena, Germany. 5 Center for Theoretical Physics of Complex Systems, Institute for Basic Science, Daejeon, 34051, Republic of Korea. -
In Situ Quantum Control Over Superconducting Qubits
! In situ quantum control over superconducting qubits Anatoly Kulikov M.Sc. A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2020 School of Mathematics and Physics ARC Centre of Excellence for Engineered Quantum Systems (EQuS) ABSTRACT In the last decade, quantum information processing has transformed from a field of mostly academic research to an applied engineering subfield with many commercial companies an- nouncing strategies to achieve quantum advantage and construct a useful universal quantum computer. Continuing efforts to improve qubit lifetime, control techniques, materials and fab- rication methods together with exploring ways to scale up the architecture have culminated in the recent achievement of quantum supremacy using a programmable superconducting proces- sor { a major milestone in quantum computing en route to useful devices. Marking the point when for the first time a quantum processor can outperform the best classical supercomputer, it heralds a new era in computer science, technology and information processing. One of the key developments enabling this transition to happen is the ability to exert more precise control over quantum bits and the ability to detect and mitigate control errors and imperfections. In this thesis, ways to efficiently control superconducting qubits are explored from the experimental viewpoint. We introduce a state-of-the-art experimental machinery enabling one to perform one- and two-qubit gates focusing on the technical aspect and outlining some guidelines for its efficient operation. We describe the software stack from the time alignment of control pulses and triggers to the data processing organisation. We then bring in the standard qubit manipulation and readout methods and proceed to describe some of the more advanced optimal control and calibration techniques. -
Simulating Quantum Field Theory with A
Simulating quantum field theory with a quantum computer PoS(LATTICE2018)024 John Preskill∗ Institute for Quantum Information and Matter Walter Burke Institute for Theoretical Physics California Institute of Technology, Pasadena CA 91125, USA E-mail: [email protected] Forthcoming exascale digital computers will further advance our knowledge of quantum chromo- dynamics, but formidable challenges will remain. In particular, Euclidean Monte Carlo methods are not well suited for studying real-time evolution in hadronic collisions, or the properties of hadronic matter at nonzero temperature and chemical potential. Digital computers may never be able to achieve accurate simulations of such phenomena in QCD and other strongly-coupled field theories; quantum computers will do so eventually, though I’m not sure when. Progress toward quantum simulation of quantum field theory will require the collaborative efforts of quantumists and field theorists, and though the physics payoff may still be far away, it’s worthwhile to get started now. Today’s research can hasten the arrival of a new era in which quantum simulation fuels rapid progress in fundamental physics. The 36th Annual International Symposium on Lattice Field Theory - LATTICE2018 22-28 July, 2018 Michigan State University, East Lansing, Michigan, USA. ∗Speaker. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). https://pos.sissa.it/ Simulating quantum field theory with a quantum computer John Preskill 1. Introduction My talk at Lattice 2018 had two main parts. In the first part I commented on the near-term prospects for useful applications of quantum computing. -
Superconducting Phase Qubits
Noname manuscript No. (will be inserted by the editor) Superconducting Phase Qubits John M. Martinis Received: date / Accepted: date Abstract Experimental progress is reviewed for superconducting phase qubit research at the University of California, Santa Barbara. The phase qubit has a potential ad- vantage of scalability, based on the low impedance of the device and the ability to microfabricate complex \quantum integrated circuits". Single and coupled qubit ex- periments, including qubits coupled to resonators, are reviewed along with a discus- sion of the strategy leading to these experiments. All currently known sources of qubit decoherence are summarized, including energy decay (T1), dephasing (T2), and mea- surement errors. A detailed description is given for our fabrication process and control electronics, which is directly scalable. With the demonstration of the basic operations needed for quantum computation, more complex algorithms are now within reach. Keywords quantum computation ¢ qubits ¢ superconductivity ¢ decoherence 1 Introduction Superconducting qubits are a unique and interesting approach to quantum computation because they naturally allow strong coupling. Compared to other qubit implementa- tions, they are physically large, from » 1 ¹m to » 100 ¹m in size, with interconnection topology and strength set by simple circuit wiring. Superconducting qubits have the advantage of scalability, as complex circuits can be constructed using well established integrated-circuit microfabrication technology. A key component of superconducting qubits is the Josephson junction, which can be thought of as an inductor with strong non-linearity and negligible energy loss. Combined with a capacitance, coming from the tunnel junction itself or an external element, a inductor-capacitor resonator is formed that exhibits non-linearity even at the single photon level.