Non-Classicality As a Computational Resource
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(CST Part II) Lecture 14: Fault Tolerant Quantum Computing
Quantum Computing (CST Part II) Lecture 14: Fault Tolerant Quantum Computing The history of the universe is, in effect, a huge and ongoing quantum computation. The universe is a quantum computer. Seth Lloyd 1 / 21 Resources for this lecture Nielsen and Chuang p474-495 covers the material of this lecture. 2 / 21 Why we need fault tolerance Classical computers perform complicated operations where bits are repeatedly \combined" in computations, therefore if an error occurs, it could in principle propagate to a huge number of other bits. Fortunately, in modern digital computers errors are so phenomenally unlikely that we can forget about this possibility for all practical purposes. Errors do, however, occur in telecommunications systems, but as the purpose of these is the simple transmittal of some information, it suffices to perform error correction on the final received data. In a sense, quantum computing is the worst of both of these worlds: errors do occur with significant frequency, and if uncorrected they will propagate, rendering the computation useless. Thus the solution is that we must correct errors as we go along. 3 / 21 Fault tolerant quantum computing set-up For fault tolerant quantum computing: We use encoded qubits, rather than physical qubits. For example we may use the 7-qubit Steane code to represent each logical qubit in the computation. We use fault tolerant quantum gates, which are defined such thata single error in the fault tolerant gate propagates to at most one error in each encoded block of qubits. By a \block of qubits", we mean (for example) each block of 7 physical qubits that represents a logical qubit using the Steane code. -
Arxiv:Quant-Ph/9705031V3 26 Aug 1997 Eddt Rvn Unu Optrfo Crashing
CALT-68-2112 QUIC-97-030 quant-ph/9705031 Reliable Quantum Computers John Preskill1 California Institute of Technology, Pasadena, CA 91125, USA Abstract The new field of quantum error correction has developed spectacularly since its origin less than two years ago. Encoded quantum information can be protected from errors that arise due to uncontrolled interactions with the environment. Recovery from errors can work effectively even if occasional mistakes occur during the recovery procedure. Furthermore, encoded quantum information can be processed without serious propagation of errors. Hence, an arbitrarily long quantum computation can be performed reliably, provided that the average probability of error per quantum gate is less than a certain critical value, the accuracy threshold. A quantum computer storing about 106 qubits, with a probability of error per quantum gate of order 10−6, would be a formidable factoring engine. Even a smaller, less accurate quantum computer would be able to perform many useful tasks. This paper is based on a talk presented at the ITP Conference on Quantum Coherence and Decoherence, 15-18 December 1996. 1 The golden age of quantum error correction Many of us are hopeful that quantum computers will become practical and useful computing devices some time during the 21st century. It is probably fair to say, though, that none of us can now envision exactly what the hardware of that machine of the future will be like; surely, it will be much different than the sort of hardware that experimental physicists are investigating these days. But of one thing we can be quite confident—that a practical quantum computer will incorporate some type of error correction into its operation. -
LI-DISSERTATION-2020.Pdf
FAULT-TOLERANCE ON NEAR-TERM QUANTUM COMPUTERS AND SUBSYSTEM QUANTUM ERROR CORRECTING CODES A Dissertation Presented to The Academic Faculty By Muyuan Li In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the School of Computational Science and Engineering Georgia Institute of Technology May 2020 Copyright c Muyuan Li 2020 FAULT-TOLERANCE ON NEAR-TERM QUANTUM COMPUTERS AND SUBSYSTEM QUANTUM ERROR CORRECTING CODES Approved by: Dr. Kenneth R. Brown, Advisor Department of Electrical and Computer Dr. C. David Sherrill Engineering School of Chemistry and Biochemistry Duke University Georgia Institute of Technology Dr. Edmond Chow Dr. Richard Vuduc School of Computational Science and School of Computational Science and Engineering Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. T.A. Brian Kennedy Date Approved: March 19, 2020 School of Physics Georgia Institute of Technology I think it is safe to say that no one understands quantum mechanics. R. P. Feynman To my family and my friends. ACKNOWLEDGEMENTS I would like to thank my advisor, Ken Brown, who has guided me through my graduate studies with his patience, wisdom, and generosity. He has always been supportive and helpful, and always makes himself available when I needed. I have been constantly inspired by his depth of knowledge in research, as well as his immense passion for life. I would also like to thank my committee members, Professors Edmond Chow, T.A. Brian Kennedy, C. David Sherrill, and Richard Vuduc, for their time and helpful sugges- tions. One half of my graduate career was spent at Georgia Tech and the other half at Duke University. -
Assessing the Progress of Trapped-Ion Processors Towards Fault-Tolerant Quantum Computation
PHYSICAL REVIEW X 7, 041061 (2017) Assessing the Progress of Trapped-Ion Processors Towards Fault-Tolerant Quantum Computation A. Bermudez,1,2 X. Xu,3 R. Nigmatullin,4,3 J. O’Gorman,3 V. Negnevitsky,5 P. Schindler,6 T. Monz,6 U. G. Poschinger,7 C. Hempel,8 J. Home,5 F. Schmidt-Kaler,7 M. Biercuk,8 R. Blatt,6,9 S. Benjamin,3 and M. Müller1 1Department of Physics, College of Science, Swansea University, Singleton Park, Swansea SA2 8PP, United Kingdom 2Instituto de Física Fundamental, IFF-CSIC, Madrid E-28006, Spain 3Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom 4Complex Systems Research Group, Faculty of Engineering and IT, The University of Sydney, Sydney, Australia 5Institute for Quantum Electronics, ETH Zürich, Otto-Stern-Weg 1, 8093 Zürich, Switzerland 6Institute for Experimental Physics, University of Innsbruck, 6020 Innsbruck, Austria 7Institut für Physik, Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany 8ARC Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, NSW 2006, Australia 9Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck, Austria (Received 24 May 2017; revised manuscript received 11 August 2017; published 13 December 2017) A quantitative assessment of the progress of small prototype quantum processors towards fault-tolerant quantum computation is a problem of current interest in experimental and theoretical quantum information science. We introduce a necessary and fair criterion for quantum error correction (QEC), which must be achieved in the development of these quantum processors before their sizes are sufficiently big to consider the well-known QEC threshold. -
Memory Cost of Quantum Contextuality
Master of Science Thesis in Physics Department of Electrical Engineering, Linköping University, 2016 Memory Cost of Quantum Contextuality Patrik Harrysson Master of Science Thesis in Physics Memory Cost of Quantum Contextuality Patrik Harrysson LiTH-ISY-EX--16/4967--SE Supervisor: Jan-Åke Larsson isy, Linköpings universitet Examiner: Jan-Åke Larsson isy, Linköpings universitet Division of Information Coding Department of Electrical Engineering Linköping University SE-581 83 Linköping, Sweden Copyright © 2016 Patrik Harrysson Abstract This is a study taking an information theoretic approach toward quantum contex- tuality. The approach is that of using the memory complexity of finite-state ma- chines to quantify quantum contextuality. These machines simulate the outcome behaviour of sequential measurements on systems of quantum bits as predicted by quantum mechanics. Of interest is the question of whether or not classical representations by finite-state machines are able to effectively represent the state- independent contextual outcome behaviour. Here we consider spatial efficiency, rather than temporal efficiency as considered by D. Gottesmana, for the partic- ular measurement dynamics in systems of quantum bits. Extensions of cases found in the adjacent study of Kleinmann et al.b are established by which upper bounds on memory complexity for particular scenarios are found. Furthermore, an optimal machine structure for simulating any n-partite system of quantum bits is found, by which a lower bound for the memory complexity is found for each n N. Within this finite-state machine approach questions of foundational concerns2 on quantum mechanics were sought to be addressed. Alas, nothing of novel thought on such concerns is here reported on. -
Entangled Many-Body States As Resources of Quantum Information Processing
ENTANGLED MANY-BODY STATES AS RESOURCES OF QUANTUM INFORMATION PROCESSING LI YING A thesis submitted for the Degree of Doctor of Philosophy CENTRE FOR QUANTUM TECHNOLOGIES NATIONAL UNIVERSITY OF SINGAPORE 2013 DECLARATION I hereby declare that the thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. LI YING 23 July 2013 Acknowledgments I am very grateful to have spent about four years at CQT working with Leong Chuan Kwek. He always brings me new ideas in science and has helped me to establish good collaborative relationships with other scien- tists. Kwek helped me a lot in my life. I am also very grateful to Simon C. Benjamin. He showd me how to do high quality researches in physics. Simon also helped me to improve my writing and presentation. I hope to have fruitful collaborations in the near future with Kwek and Simon. For my project about the ground-code MBQC (Chapter2), I am thank- ful to Tzu-Chieh Wei, Daniel E. Browne and Robert Raussendorf. In one afternoon, Tzu-Chieh showed me the idea of his recent paper in this topic in the quantum cafe, which encouraged me to think about the ground- code MBQC. Dan and Robert have a high level of comprehension on the subject of the MBQC. And we had some very interesting discussions and communications. I am grateful to Sean D. -
Lecture 8 Measurement-Based Quantum Computing
Introduction to quantum computation and simulability Ernesto F. Galvão Instituto de Física, Universidade Federal Fluminense (Niterói, Brazil) 1−ε 0 + ε 1 q = ε p 0 p 0 U ! 0 ICTP-SAIFR – IFT/UNESP , October 15th-19th, 2018 Introduction to quantum computation and simulability Lecture 8 : Measurement-based QC (MBQC) II Outline: • Applications of MBQC: • models for quantum spacetime • blind quantum computation • Time-ordering in MBQC • MBQC without adaptativity: • Clifford circuits • IQP circuits • Introduction to quantum contextuality • Contextuality as a computational resource • in magic state distillation • in MBQC • For slides and links to related material, see Application: blind quantum computation • Classical/quantum separation in MBQC allow for implementation of novel protocols – such as blind quantum computation • Here, client has limited quantum capabilities, and uses a server to do computation for her. • Blind = server doesn’t know what’s being computed. Broadbent, Fitzsimons, Kashefi, axiv:0807.4154 [quant-ph] Application: model for quantum spacetime • MBQC can serve as a discrete toy model for quantum spacetime: quantum space-time MBQC quantum substrate graph states events measurements principle establishing global determinism requirement space-time structure for computations [Raussendorf et al., arxiv:1108.5774] • Even closed timelike curves (= time travel) have analogues in MBQC! [Dias da Silva, Kashefi, Galvão PRA 83, 012316 (2011)] Time-ordering in MBQC from: Proc. Int. School of Physics "Enrico Fermi" on "Quantum Computers, -
Classical Zero-Knowledge Arguments for Quantum Computations
Classical zero-knowledge arguments for quantum computations Thomas Vidick∗ Tina Zhangy Abstract We show that every language in BQP admits a classical-verifier, quantum-prover zero-knowledge ar- gument system which is sound against quantum polynomial-time provers and zero-knowledge for classical (and quantum) polynomial-time verifiers. The protocol builds upon two recent results: a computational zero-knowledge proof system for languages in QMA, with a quantum verifier, introduced by Broadbent et al. (FOCS 2016), and an argument system for languages in BQP, with a classical verifier, introduced by Mahadev (FOCS 2018). 1 Introduction The paradigm of the interactive proof system is a versatile tool in complexity theory. Although traditional complexity classes are usually defined in terms of a single Turing machine|NP, for example, can be defined as the class of languages which a non-deterministic Turing machine is able to decide|many have reformulations in the language of interactive proofs, and such reformulations often inspire natural and fruitful variants on the traditional classes upon which they are based. (The class MA, for example, can be considered a natural extension of NP under the interactive-proof paradigm.) Intuitively speaking, an interactive proof system is a model of computation involving two entities, a verifier and a prover, the former of whom is computationally efficient, and the latter of whom is unbounded but untrusted. The verifier and the prover exchange messages, and the prover attempts to `convince' the verifier that a certain problem instance is a yes-instance. We can define some particular complexity class as the set of languages for which there exists an interactive proof system that 1) is complete, 2) is sound, and 3) has certain other properties which vary depending on the class in question. -
G53NSC and G54NSC Non Standard Computation Research Presentations
G53NSC and G54NSC Non Standard Computation Research Presentations March the 23rd and 30th, 2010 Tuesday the 23rd of March, 2010 11:00 - James Barratt • Quantum error correction 11:30 - Adam Christopher Dunkley and Domanic Nathan Curtis Smith- • Jones One-Way quantum computation and the Measurement calculus 12:00 - Jack Ewing and Dean Bowler • Physical realisations of quantum computers Tuesday the 30th of March, 2010 11:00 - Jiri Kremser and Ondrej Bozek Quantum cellular automaton • 11:30 - Andrew Paul Sharkey and Richard Stokes Entropy and Infor- • mation 12:00 - Daniel Nicholas Kiss Quantum cryptography • 1 QUANTUM ERROR CORRECTION JAMES BARRATT Abstract. Quantum error correction is currently considered to be an extremely impor- tant area of quantum computing as any physically realisable quantum computer will need to contend with the issues of decoherence and other quantum noise. A number of tech- niques have been developed that provide some protection against these problems, which will be discussed. 1. Introduction It has been realised that the quantum mechanical behaviour of matter at the atomic and subatomic scale may be used to speed up certain computations. This is mainly due to the fact that according to the laws of quantum mechanics particles can exist in a superposition of classical states. A single bit of information can be modelled in a number of ways by particles at this scale. This leads to the notion of a qubit (quantum bit), which is the quantum analogue of a classical bit, that can exist in the states 0, 1 or a superposition of the two. A number of quantum algorithms have been invented that provide considerable improvement on their best known classical counterparts, providing the impetus to build a quantum computer. -
Arxiv:0905.2794V4 [Quant-Ph] 21 Jun 2013 Error Correction 7 B
Quantum Error Correction for Beginners Simon J. Devitt,1, ∗ William J. Munro,2 and Kae Nemoto1 1National Institute of Informatics 2-1-2 Hitotsubashi Chiyoda-ku Tokyo 101-8340. Japan 2NTT Basic Research Laboratories NTT Corporation 3-1 Morinosato-Wakamiya, Atsugi Kanagawa 243-0198. Japan (Dated: June 24, 2013) Quantum error correction (QEC) and fault-tolerant quantum computation represent one of the most vital theoretical aspect of quantum information processing. It was well known from the early developments of this exciting field that the fragility of coherent quantum systems would be a catastrophic obstacle to the development of large scale quantum computers. The introduction of quantum error correction in 1995 showed that active techniques could be employed to mitigate this fatal problem. However, quantum error correction and fault-tolerant computation is now a much larger field and many new codes, techniques, and methodologies have been developed to implement error correction for large scale quantum algorithms. In response, we have attempted to summarize the basic aspects of quantum error correction and fault-tolerance, not as a detailed guide, but rather as a basic introduction. This development in this area has been so pronounced that many in the field of quantum information, specifically researchers who are new to quantum information or people focused on the many other important issues in quantum computation, have found it difficult to keep up with the general formalisms and methodologies employed in this area. Rather than introducing these concepts from a rigorous mathematical and computer science framework, we instead examine error correction and fault-tolerance largely through detailed examples, which are more relevant to experimentalists today and in the near future. -
On Graph Approaches to Contextuality and Their Role in Quantum Theory
SPRINGER BRIEFS IN MATHEMATICS Barbara Amaral · Marcelo Terra Cunha On Graph Approaches to Contextuality and their Role in Quantum Theory 123 SpringerBriefs in Mathematics Series editors Nicola Bellomo Michele Benzi Palle Jorgensen Tatsien Li Roderick Melnik Otmar Scherzer Benjamin Steinberg Lothar Reichel Yuri Tschinkel George Yin Ping Zhang SpringerBriefs in Mathematics showcases expositions in all areas of mathematics and applied mathematics. Manuscripts presenting new results or a single new result in a classical field, new field, or an emerging topic, applications, or bridges between new results and already published works, are encouraged. The series is intended for mathematicians and applied mathematicians. More information about this series at http://www.springer.com/series/10030 SBMAC SpringerBriefs Editorial Board Carlile Lavor University of Campinas (UNICAMP) Institute of Mathematics, Statistics and Scientific Computing Department of Applied Mathematics Campinas, Brazil Luiz Mariano Carvalho Rio de Janeiro State University (UERJ) Department of Applied Mathematics Graduate Program in Mechanical Engineering Rio de Janeiro, Brazil The SBMAC SpringerBriefs series publishes relevant contributions in the fields of applied and computational mathematics, mathematics, scientific computing, and related areas. Featuring compact volumes of 50 to 125 pages, the series covers a range of content from professional to academic. The Sociedade Brasileira de Matemática Aplicada e Computacional (Brazilian Society of Computational and Applied Mathematics, -
Non-Deterministic Semantics for Quantum States
entropy Article Non-Deterministic Semantics for Quantum States Juan Pablo Jorge 1 and Federico Holik 2,* 1 Physics Department, University of Buenos Aires, Buenos Aires 1428, Argentina; [email protected] 2 Instituto de Física La Plata, UNLP, CONICET, Facultad de Ciencias Exactas, 1900 La Plata, Argentina * Correspondence: [email protected] Received: 16 October 2019; Accepted: 27 January 2020; Published: 28 January 2020 Abstract: In this work, we discuss the failure of the principle of truth functionality in the quantum formalism. By exploiting this failure, we import the formalism of N-matrix theory and non-deterministic semantics to the foundations of quantum mechanics. This is done by describing quantum states as particular valuations associated with infinite non-deterministic truth tables. This allows us to introduce a natural interpretation of quantum states in terms of a non-deterministic semantics. We also provide a similar construction for arbitrary probabilistic theories based in orthomodular lattices, allowing to study post-quantum models using logical techniques. Keywords: quantum states; non-deterministic semantics; truth functionality 1. Introduction According to the principle of truth-functionality or composability (TFP), the truth-value of a complex formula is uniquely determined by the truth-values of its subformulas. It is a basic principle of logic. However, as explained in [1], many real-world situations involve dealing with information that is incomplete, vague or uncertain. This is especially true for quantum phenomena, where only probabilistic assertions about possible events can be tested in the lab. These situations pose a threat to the application of logical systems obeying the principle of truth-functionality in those problems.