Real-Time Processing of Stabilizer Measurements in a Bit-Flip Code
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Programm 5 Layout 1
SPONSORS Pauli Center for Theoretical Studies QAP European Project PAULI CENTER for Theoretical Studies Sandia National Laboratories The Swiss National Science Foundation Institute for Quantum Computing ETH Zurich (Computer Science and Physics Department) id Quantique Quantum Science and Technology (ETH) CQT Singapore VENUE W-LAN ETH Zürich, Rämistrasse 101, CH-8092 Zürich 1. Check available WLAN’s Main building / Hauptgebäude 2. Connect to WLAN „public“ Conference Helpline 0041 (0)79 770 84 29 3. Open browser 4.Login at welcome page with Login: qip2010 Password: 2010qipconf Main entrance FLOOR E Registration/Information desk Poster session Computer room E 26.3 Main entrance Registration desk Information Computer room E 26.3 Poster session 1 FLOOR E. 0 Poster session FLOOR F Auditorium F 5: Tutorial (January 15 – 17, 2010) Auditorium maximum F 30: Scientific programme (January 18 – 22, 2010) F 33.1: Congress-Office, F 33.2: Cloak room Foyer and “Uhrenhalle”: Coffee breaks, Poster session Auditorium Maximum F 30 Scientific programmme January 18 – 22, 2010 F 33.1: Congress-Office Foyer: F 33.2 Cloak room Coffee breaks Poster session Auditorium F 5 Tutorial January 15 – 17, 2010 Uhrenhalle: Coffee breaks 2 RUMP SESSION StuZ, ETH Zürich, Universitätsstrasse 6, CH-8092 Zürich CAB Building room No. CAB F21 to CAB F27 18.30 – 23.00 h (January 20, 2010) Entry ETH CAB Building ETH Main Building 3 CONFERENCE DINNER Thursday, January 21, 2010, 19.00h Restaurant Lake Side Bellerivestrasse 170 CH-8008 Zürich Phone: +41 (0) 44 385 86 00 Directions from ETH main building • (Tram No. 9 to “Bellevue” (direction “Triemli”). -
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. -
Using Graph States for Quantum Computation and Communication
Using Graph States for Quantum Computation and Communication Thesis by Kovid Goyal In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2009 (Submitted May 27, 2009) ii c 2009 Kovid Goyal All Rights Reserved iii To Dr. Ajay Patwardhan, for inspiring a whole generation of physicists. iv Acknowledgements I would like to start by acknowledging my thesis adviser, John Preskill, for giving me the freedom to pursue my interests and for setting a very high standard for me to aspire to. John has also provided the direction I needed at critical points in my career. I would like to thank Robert Raussendorf for sharing a lot of his ideas with me and patiently explaining them when needed. Most of the great ideas in Chapter 2 were orig- inated by him. Robert has been a mentor and a guide. I would like to thank Jim Harrington for introducing me to the numerical techniques needed for the analysis of the measurement based quantum computer and for writing relatively clear and easy to follow code. I would like to thank Austin Fowler for asking me a lot of questions and thereby greatly improving the clarity and depth of my understanding. Austin also inspired me to make this work as clear and easy to follow as possible. The magic state distillation circuit diagrams and the CNOT gate construction in Chapter 2 are his. I would like to thank Ben Toner, Panos Aliferis, Greg Ver Steeg and Prabha Mandayam Dodamanne for many stimulating discussions. I would like to thank my parents, Ashima and Niraj, for supporting my desire to be- come a physicist and for providing me with a stimulating and enjoyable childhood. -
Booklet of Abstracts
Booklet of abstracts Thomas Vidick California Institute of Technology Tsirelson's problem and MIP*=RE Boris Tsirelson in 1993 implicitly posed "Tsirelson's Problem", a question about the possible equivalence between two different ways of modeling locality, and hence entanglement, in quantum mechanics. Tsirelson's Problem gained prominence through work of Fritz, Navascues et al., and Ozawa a decade ago that establishes its equivalence to the famous "Connes' Embedding Problem" in the theory of von Neumann algebras. Recently we gave a negative answer to Tsirelson's Problem and Connes' Embedding Problem by proving a seemingly stronger result in quantum complexity theory. This result is summarized in the equation MIP* = RE between two complexity classes. In the talk I will present and motivate Tsirelson's problem, and outline its connection to Connes' Embedding Problem. I will then explain the connection to quantum complexity theory and show how ideas developed in the past two decades in the study of classical and quantum interactive proof systems led to the characterization (which I will explain) MIP* = RE and the negative resolution of Tsirelson's Problem. Based on joint work with Ji, Natarajan, Wright and Yuen available at arXiv:2001.04383. Joonho Lee, Dominic Berry, Craig Gidney, William Huggins, Jarrod McClean, Nathan Wiebe and Ryan Babbush Columbia University | Macquarie University | Google | Google Research | Google | University of Washington | Google Efficient quantum computation of chemistry through tensor hypercontraction We show how to achieve the highest efficiency yet for simulations with arbitrary basis sets by using a representation of the Coulomb operator known as tensor hypercontraction (THC). We use THC to express the Coulomb operator in a non-orthogonal basis, which we are able to block encode by separately rotating each term with angles that are obtained via QROM. -
Universal Control and Error Correction in Multi-Qubit Spin Registers in Diamond T
LETTERS PUBLISHED ONLINE: 2 FEBRUARY 2014 | DOI: 10.1038/NNANO.2014.2 Universal control and error correction in multi-qubit spin registers in diamond T. H. Taminiau 1,J.Cramer1,T.vanderSar1†,V.V.Dobrovitski2 and R. Hanson1* Quantum registers of nuclear spins coupled to electron spins of including one with an additional strongly coupled 13C spin (see individual solid-state defects are a promising platform for Supplementary Information). To demonstrate the generality of quantum information processing1–13. Pioneering experiments our approach to create multi-qubit registers, we realized the initia- selected defects with favourably located nuclear spins with par- lization, control and readout of three weakly coupled 13C spins for ticularly strong hyperfine couplings4–10. To progress towards each NV centre studied (see Supplementary Information). In the large-scale applications, larger and deterministically available following, we consider one of these NV centres in detail and use nuclear registers are highly desirable. Here, we realize univer- two of its weakly coupled 13C spins to form a three-qubit register sal control over multi-qubit spin registers by harnessing abun- for quantum error correction (Fig. 1a). dant weakly coupled nuclear spins. We use the electron spin of Our control method exploits the dependence of the nuclear spin a nitrogen–vacancy centre in diamond to selectively initialize, quantization axis on the electron spin state as a result of the aniso- control and read out carbon-13 spins in the surrounding spin tropic hyperfine interaction (see Methods for hyperfine par- bath and construct high-fidelity single- and two-qubit gates. ameters), so no radiofrequency driving of the nuclear spins is We exploit these new capabilities to implement a three-qubit required7,23–28. -
1 Objectives of the Workshop 2 Open Problem Discussion
Final Report: BIRS Workshop 16w5029 Quantum Computer Science April 17–22, 2016 Co-organizers: Michele Mosca, Martin Roetteler, and Peter Selinger 1 Objectives of the workshop Shor’s famous quantum algorithms for integer factoring and to compute discrete logarithms helped to kick-start the field of quantum computing. A topic that has received significantly less attention is that of actually translating quantum algorithms into elementary instructions that can then be carried out on a future large-scale quantum computer. This leads to questions about automation of the translation process, a question that gives rise to several challenges that arise naturally from there, for instance: how to program a quantum computer? How to model the underlying instructions? How to compile and optimize code that has been written in a high level of abstraction? This interdisciplinary workshop aimed at making progress on these questions and brought to- gether over 40 researchers from a diverse set of research communities: those working in quan- tum computing, and those working on the mathematical foundations of programming languages and their implementations. We anticipate a vibrant exchange of novel ideas, to tackle important problems such as the optimization of large-scale quantum algorithms, and their synthesis into the instruction set of a fault-tolerant quantum computer. On the first day there was a very lively open problems debate, a summary of which is provided in this report. The problems ranged from big challenges that likely will remain open for some time, to concrete problems, some of which were tackled during the workshop. Besides the open problem discussion and a plethora of talks on recent topics of interests, salient features of the workshop were various software demo sessions in which some of the participants performed live demos of their software programs, and two tutorials about quantum programming languages. -
Unconditional Quantum Teleportation
R ESEARCH A RTICLES our experiment achieves Fexp 5 0.58 6 0.02 for the field emerging from Bob’s station, thus Unconditional Quantum demonstrating the nonclassical character of this experimental implementation. Teleportation To describe the infinite-dimensional states of optical fields, it is convenient to introduce a A. Furusawa, J. L. Sørensen, S. L. Braunstein, C. A. Fuchs, pair (x, p) of continuous variables of the electric H. J. Kimble,* E. S. Polzik field, called the quadrature-phase amplitudes (QAs), that are analogous to the canonically Quantum teleportation of optical coherent states was demonstrated experi- conjugate variables of position and momentum mentally using squeezed-state entanglement. The quantum nature of the of a massive particle (15). In terms of this achieved teleportation was verified by the experimentally determined fidelity analogy, the entangled beams shared by Alice Fexp 5 0.58 6 0.02, which describes the match between input and output states. and Bob have nonlocal correlations similar to A fidelity greater than 0.5 is not possible for coherent states without the use those first described by Einstein et al.(16). The of entanglement. This is the first realization of unconditional quantum tele- requisite EPR state is efficiently generated via portation where every state entering the device is actually teleported. the nonlinear optical process of parametric down-conversion previously demonstrated in Quantum teleportation is the disembodied subsystems of infinite-dimensional systems (17). The resulting state corresponds to a transport of an unknown quantum state from where the above advantages can be put to use. squeezed two-mode optical field. -
A Practical Phase Gate for Producing Bell Violations in Majorana Wires
PHYSICAL REVIEW X 6, 021005 (2016) A Practical Phase Gate for Producing Bell Violations in Majorana Wires David J. Clarke, Jay D. Sau, and Sankar Das Sarma Department of Physics, Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742, USA and Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA (Received 9 October 2015; published 8 April 2016) Carrying out fault-tolerant topological quantum computation using non-Abelian anyons (e.g., Majorana zero modes) is currently an important goal of worldwide experimental efforts. However, the Gottesman- Knill theorem [1] holds that if a system can only perform a certain subset of available quantum operations (i.e., operations from the Clifford group) in addition to the preparation and detection of qubit states in the computational basis, then that system is insufficient for universal quantum computation. Indeed, any measurement results in such a system could be reproduced within a local hidden variable theory, so there is no need for a quantum-mechanical explanation and therefore no possibility of quantum speedup [2]. Unfortunately, Clifford operations are precisely the ones available through braiding and measurement in systems supporting non-Abelian Majorana zero modes, which are otherwise an excellent candidate for topologically protected quantum computation. In order to move beyond the classically simulable subspace, an additional phase gate is required. This phase gate allows the system to violate the Bell-like Clauser- Horne-Shimony-Holt (CHSH) inequality that would constrain a local hidden variable theory. In this article, we introduce a new type of phase gate for the already-existing semiconductor-based Majorana wire systems and demonstrate how this phase gate may be benchmarked using CHSH measurements. -
Quantum Error Modelling and Correction in Long Distance Teleportation Using Singlet States by Joe Aung
Quantum Error Modelling and Correction in Long Distance Teleportation using Singlet States by Joe Aung Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering and Computer Science at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May 2002 @ Massachusetts Institute of Technology 2002. All rights reserved. Author ................... " Department of Electrical Engineering and Computer Science May 21, 2002 72-1 14 Certified by.................. .V. ..... ..'P . .. ........ Jeffrey H. Shapiro Ju us . tn Professor of Electrical Engineering Director, Research Laboratory for Electronics Thesis Supervisor Accepted by................I................... ................... Arthur C. Smith Chairman, Department Committee on Graduate Students BARKER MASSACHUSE1TS INSTITUTE OF TECHNOLOGY JUL 3 1 2002 LIBRARIES 2 Quantum Error Modelling and Correction in Long Distance Teleportation using Singlet States by Joe Aung Submitted to the Department of Electrical Engineering and Computer Science on May 21, 2002, in partial fulfillment of the requirements for the degree of Master of Science in Electrical Engineering and Computer Science Abstract Under a multidisciplinary university research initiative (MURI) program, researchers at the Massachusetts Institute of Technology (MIT) and Northwestern University (NU) are devel- oping a long-distance, high-fidelity quantum teleportation system. This system uses a novel ultrabright source of entangled photon pairs and trapped-atom quantum memories. This thesis will investigate the potential teleportation errors involved in the MIT/NU system. A single-photon, Bell-diagonal error model is developed that allows us to restrict possible errors to just four distinct events. The effects of these errors on teleportation, as well as their probabilities of occurrence, are determined. -
Limitations on Transversal Computation Through Quantum
Limitations on Transversal Computation through Quantum Homomorphic Encryption Michael Newman1 and Yaoyun Shi2 1Department of Mathematics 2Department of Electrical Engineering and Computer Science University of Michigan, Ann Arbor, MI 48109, USA [email protected], [email protected] Abstract Transversality is a simple and effective method for implementing quantum computation fault- tolerantly. However, no quantum error-correcting code (QECC) can transversally implement a quantum universal gate set (Eastin and Knill, Phys. Rev. Lett., 102, 110502). Since reversible classical computation is often a dominating part of useful quantum computation, whether or not it can be implemented transversally is an important open problem. We show that, other than a small set of non-additive codes that we cannot rule out, no binary QECC can transversally implement a classical reversible universal gate set. In particular, no such QECC can implement the Toffoli gate transversally. We prove our result by constructing an information theoretically secure (but inefficient) quan- tum homomorphic encryption (ITS-QHE) scheme inspired by Ouyang et al. (arXiv:1508.00938). Homomorphic encryption allows the implementation of certain functions directly on encrypted data, i.e. homomorphically. Our scheme builds on almost any QECC, and implements that code’s transversal gate set homomorphically. We observe a restriction imposed by Nayak’s bound (FOCS 1999) on ITS-QHE, implying that any ITS quantum fully homomorphic scheme (ITS-QFHE) implementing the full set of classical reversible functions must be highly ineffi- cient. While our scheme incurs exponential overhead, any such QECC implementing Toffoli transversally would still violate this lower bound through our scheme. arXiv:1704.07798v3 [quant-ph] 13 Aug 2017 1 Introduction 1.1 Restrictions on transversal gates Transversal gates are surprisingly ubiquitous objects, finding applications in quantum cryptography [29], [25], quantum complexity theory [11], and of course quantum fault-tolerance. -
Quantum Machine Learning and Quantum Biomimetics: a Perspective
Quantum machine learning and quantum biomimetics: A perspective Lucas Lamata Departamento de F´ısicaAt´omica, Molecular y Nuclear, Universidad de Sevilla, 41080 Sevilla, Spain April 2020 Abstract. Quantum machine learning has emerged as an exciting and promising paradigm inside quantum technologies. It may permit, on the one hand, to carry out more efficient machine learning calculations by means of quantum devices, while, on the other hand, to employ machine learning techniques to better control quantum systems. Inside quantum machine learning, quantum reinforcement learning aims at developing \intelligent" quantum agents that may interact with the outer world and adapt to it, with the strategy of achieving some final goal. Another paradigm inside quantum machine learning is that of quantum autoencoders, which may allow one for employing fewer resources in a quantum device via a training process. Moreover, the field of quantum biomimetics aims at establishing analogies between biological and quantum systems, to look for previously inadvertent connections that may enable useful applications. Two recent examples are the concepts of quantum artificial life, as well as of quantum memristors. In this Perspective, we give an overview of these topics, describing the related research carried out by the scientific community. Keywords: Quantum machine learning; quantum biomimetics; quantum artificial intelligence; quantum reinforcement learning; quantum autoencoders; quantum artificial life; quantum memristors arXiv:2004.12076v2 [quant-ph] 30 May 2020 1. Introduction The field of quantum technologies has experienced a significant boost in the past five years. The interest of multinational companies such as Google, IBM, Microsoft, Intel, and Alibaba in this area has increased the worldwide competition and available funding not only from these firms, but also from national and supranational governments, such as the European Union [1, 2]. -
Phd Proposal 2020: Quantum Error Correction with Superconducting Circuits
PhD Proposal 2020: Quantum error correction with superconducting circuits Keywords: quantum computing, quantum error correction, Josephson junctions, circuit quantum electrodynamics, high-impedance circuits • Laboratory name: Laboratoire de Physique de l'Ecole Normale Supérieure de Paris • PhD advisors : Philippe Campagne-Ibarcq ([email protected]) and Zaki Leghtas ([email protected]). • Web pages: http://cas.ensmp.fr/~leghtas/ https://philippecampagneib.wixsite.com/research • PhD location: ENS Paris, 24 rue Lhomond Paris 75005. • Funding: ERC starting grant. Quantum systems can occupy peculiar states, such as superpositions or entangled states. These states are intrinsically fragile and eventually get wiped out by inevitable interactions with the environment. Protecting quantum states against decoherence is a formidable and fundamental problem in physics, and it is pivotal for the future of quantum computing. Quantum error correction provides a potential solution, but its current envisioned implementations require daunting resources: a single bit of information is protected by encoding it across tens of thousands of physical qubits. Our team in Paris proposes to protect quantum information in an entirely new type of qubit with two key specicities. First, it will be encoded in a single superconducting circuit resonator whose innite dimensional Hilbert space can replace large registers of physical qubits. Second, this qubit will be rf-powered, continuously exchanging photons with a reservoir. This approach challenges the intuition that a qubit must be isolated from its environment. Instead, the reservoir acts as a feedback loop which continuously and autonomously corrects against errors. This correction takes place at the level of the quantum hardware, and reduces the need for error syndrome measurements which are resource intensive.