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Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks

Physical Review A 2009年第1期79卷 012307-012307页

作者： Yi-Bo Zhao Matthias Heid Johannes Rigas Norbert Lütkenhaus Key Lab of Quantum Information University of Science and Technology of China (CAS) Hefei Anhui 230026 China Quantum Information Theory Group Institut für Theoretische Physik I and Max-Planck Research Group Institute of Optics Information and Photonics Universität Erlangen-Nürnberg Staudtstraße 7/B2 91058 Erlangen Germany Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo 200 University Ave. West Waterloo Ontario Canada N2L 3G1 Departamento de Óptica Facultad de Física Universidad Complutense 28040 Madrid Spain

We estimate a lower bound to the secret key rate of a binary modulated continuous variable quantum key distribution scheme. We consider the collective attack scenario with quantum channels that impose arbitrary noise on the exchanged signals. The analysis is done in the infinite key limit. Bob performs ideal homodyne measurements on the received states and the two honest parties employ a reverse reconciliation procedure in the classical postprocessing step of the protocol.

关键词： cryptographic protocols homodyne detection quantum cryptography telecommunication security STATES

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Unconditional security of the Bennett 1992 quantum-key-distribution scheme with a strong reference pulse

引用

Physical Review A 2009年第3期80卷 032302-032302页

作者： Kiyoshi Tamaki Norbert Lütkenhaus Masato Koashi Jamie Batuwantudawe NTT Basic Research Laboratories NTT Corporation 3-1 Morinosato Wakamiya Atsugi-Shi Kanagawa 243-0198 Japan CREST JST Agency 4-1-8 Honcho Kawaguchi Saitama 332-0012 Japan Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada N2L 3G1 Quantum Information Theory Group Institut für Theoretische Physik Universität Erlangen-Nürnberg Staudtstr. 7/B3 91058 Erlangen Germany Department of Materials Engineering Science Graduate School of Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan

We prove the unconditional security of the original Bennett 1992 protocol with strong reference pulse. We show that we may place a projection onto suitably defined qubit spaces before the receiver, which makes the analysis as simple as qubit-based protocols. Unlike the single-photon-based qubits, the qubits identified in this scheme are almost surely detected by the receiver even after a lossy channel. This leads to the key generation rate that is proportional to the channel transmission rate for proper choices of experimental parameters.

关键词： Particle beams

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quantum teleportation of wavepackets in a non-Gaussian state

Quantum teleportation of wavepackets in a non-Gaussian state

引用

Conference on Lasers and Electro-Optics (CLEO)

作者： Noriyuki Lee Yuishi Takeno Hugo Benichi Hidehiro Yonezawa James Webb Elanor Huntington Ladislav Mista Radim Filip Peter van Loock Samuel L. Braunstein Akira Furusawa Department of Applied Physics School of Engineering University of Tokyo Bunkyo Tokyo Japan CREST Japan Science and Technology Agency Chuo Tokyo Japan Centre for Quantum Computer Technology School of Information Technology and Electrical Engineering University College University of New South Wales Canberra ACT Australia Department of Optics Palacký University Olomouc Czech Republic Optical Quantum Information Theory Group Institute of Theoretical Physics I and Max-Planck Research Group Institute of Optics Information and Photonics Universität Erlangen Nürnberg Erlangen Germany Computer Science University of York York UK

We demonstrate quantum teleportation of wavepackets in a non-Gaussian state, so-called ldquoSchroumldinger kittenrdquo, for the first time.

关键词： Teleportation quantum computing quantum mechanics Information processing Paramagnetic resonance Optical filters Optical pumping Physics Protocols Delay lines

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Distinguishing short quantum computations

Distinguishing short quantum computations

引用

25th International Symposium on Theoretical Aspects of computer science, STACS 2008

作者： Rosgen, Bill Institute for Quantum Computing School of Computer Science University of Waterloo

ISBN: (纸本)9783939897064

Distinguishing logarithmic depth quantum circuits on mixed states is shown to be complete for QIP, the class of problems having quantum interactive proof systems. Circuits in this model can represent arbitrary quantum processes, and thus this result has implications for the verification of implementations of quantum algorithms. The distinguishability problem is also complete for QIP on constant depth circuits containing the unbounded fan-out gate. These results are shown by reducing a QIP-complete problem to a logarithmic depth version of itself using a parallelization technique.

关键词： Timing circuits

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Assessing the performance of recent density functionals for bulk solids

引用

Physical Review B 2009年第15期79卷 155107-155107页

作者： Gábor I. Csonka John P. Perdew Adrienn Ruzsinszky Pier H. T. Philipsen Sébastien Lebègue Joachim Paier Oleg A. Vydrov János G. Ángyán Department of Inorganic and Analytical Chemistry Budapest University of Technology and Economics H-1521 Budapest Hungary Department of Physics and Quantum Theory Group Tulane University New Orleans Louisiana 70118 USA Scientific Computing and Modelling NV Theoretical Chemistry Vrije Universiteit De Boelelaan 1083 1081 HV Amsterdam The Netherlands CRM2 UMR 7036 Institut Jean Barriol Nancy-University and CNRS Boîte Postale 239 F-54506 Vandoeuvre-lès-Nancy France Faculty of Physics Center for Computational Materials Science Universität Wien Sensengasse 8/12 A-1090 Wien Austria Department of Chemistry Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

We assess the performance of recent density functionals for the exchange-correlation energy of a nonmolecular solid, by applying accurate calculations with the GAUSSIAN, BAND, and VASP codes to a test set of 24 solid metals and nonmetals. The functionals tested are the modified Perdew-Burke-Ernzerhof generalized gradient approximation (PBEsol GGA), the second-order GGA (SOGGA), and the Armiento-Mattsson 2005 (AM05) GGA. For completeness, we also test more standard functionals: the local density approximation, the original PBE GGA, and the Tao-Perdew-Staroverov-Scuseria meta-GGA. We find that the recent density functionals for solids reach a high accuracy for bulk properties (lattice constant and bulk modulus). For the cohesive energy, PBE is better than PBEsol overall, as expected, but PBEsol is actually better for the alkali metals and alkali halides. For fair comparison of calculated and experimental results, we consider the zero-point phonon and finite-temperature effects ignored by many workers. We show how GAUSSIAN basis sets and inaccurate experimental reference data may affect the rating of the quality of the functionals. The results show that PBEsol and AM05 perform somewhat differently from each other for alkali metal, alkaline-earth metal, and alkali halide crystals (where the maximum value of the reduced density gradient is about 2), but perform very similarly for most of the other solids (where it is often about 1). Our explanation for this is consistent with the importance of exchange-correlation nonlocality in regions of core-valence overlap.

关键词： binding energy density functional theory elastic moduli lattice constants phonons

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Pion form factors from two-flavor lattice QCD with exact chiral symmetry

引用

Physical Review D 2009年第3期80卷 034508-034508页

作者： S. Aoki T. W. Chiu H. Fukaya S. Hashimoto T. H. Hsieh T. Kaneko H. Matsufuru J. Noaki T. Onogi E. Shintani N. Yamada Graduate School of Pure and Applied Sciences University of Tsukuba Ibaraki 305-8571 Japan Riken BNL Research Center Brookhaven National Laboratory Upton New York 11973 USA Physics Department Center for Theoretical Sciences and Center for Quantum Science and Engineering National Taiwan University Taipei 10617 Taiwan Department of Physics Nagoya University Nagoya 464-8602 Japan KEK Theory Center High Energy Accelerator Research Organization (KEK) Ibaraki 305-0801 Japan School of High Energy Accelerator Science The Graduate University for Advanced Studies (Sokendai) Ibaraki 305-0801 Japan Research Center for Applied Sciences Academia Sinica Taipei 115 Taiwan Computing Research Center High Energy Accelerator Research Organization (KEK) Ibaraki 305-0801 Japan Yukawa Institute for Theoretical Physics Kyoto University Kyoto 606-8502 Japan

We calculate pion vector and scalar form factors in two-flavor lattice QCD and study the chiral behavior of the vector and scalar radii ⟨r2⟩V,S. Numerical simulations are carried out on a 163×32 lattice at a lattice spacing of 0.12 fm with quark masses down to ∼ms/6, where ms is the physical strange quark mass. Chiral symmetry, which is essential for a direct comparison with chiral perturbation theory (ChPT), is exactly preserved in our calculation at finite lattice spacing by employing the overlap quark action. We utilize the so-called all-to-all quark propagator in order to calculate the scalar form factor including the contributions of disconnected diagrams and to improve statistical accuracy of the form factors. A detailed comparison with ChPT reveals that the next-to-next-to-leading-order contributions to the radii are essential to describe their chiral behavior in the region of quark mass from ms/6 to ms/2. Chiral extrapolation based on two-loop ChPT yields ⟨r2⟩V=0.409(23)(37) fm2 and ⟨r2⟩S=0.617(79)(66) fm2, which are consistent with phenomenological analysis. We also present our estimates of relevant low-energy constants.

关键词：

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An exponential separation between the entanglement and communication capacities of a bipartite unitary interaction

An exponential separation between the entanglement and commu...

引用

International Conference on quantum Information, ICQI 2008

作者： Harrow, Aram W. Leung, Debbie W. Department of Computer Science University of Bristol Bristol BS8 1UB United Kingdom Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3G1 Canada

We consider asymptotic capacities of bipartite unitary gates. We present a gate with exponen- tially larger entanglement capacity than the total communication capacity. The key tool is a communication- efficient metho... 详细信息

关键词： quantum optics

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An exponential separation between the entanglement and communication capacities of a bipartite unitary interaction

An exponential separation between the entanglement and commu...

引用

IEEE (first ITW conference of the year) Information theory Workshop (ITW)

作者： Aram W. Harrow Debbie W. Leung Department of Computer Science University of Bristol Bristol UK Department of Combinatorics and Optimization and Institute for Quantum Computing University of Waterloo Waterloo ONT Canada

We consider asymptotic capacities of bipartite unitary gates. We present a gate with exponentially larger entanglement capacity than the total communication capacity. The key tool in our proof, which may be of independent interest, is a communication-efficient protocol for testing whether a bipartite quantum state belongs to a short list of candidate states.

关键词： quantum entanglement quantum computing Protocols Paramagnetic resonance computer science Combinatorial mathematics Testing Information processing Communication channels Tensile stress

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quantum circuit placement

Quantum circuit placement

引用

作者： Maslov, Dmitri Falconer, Sean M. Mosca, Michele Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo Waterloo ON N2L 3G1 Canada Department of Computer Science University of Victoria Victoria BC V8W 3P6 Canada St. Jerome's University Waterloo ON N2L 3G3 Canada Perimeter Institute for Theoretical Physics Waterloo ON N2L 2Y5 Canada

We study the problem of the practical realization of an abstract quantum circuit when executed on a quantum hardware. By practical, we mean adapting the circuit to particulars of the physical environment which restricts/complicates the establishment of certain direct interactions between qubits. This is a quantum version of the classical circuit placement problem. We study the theoretical aspects of the problem and also present empirical results that match the best known solutions that have been developed by experimentalists. Finally, we discuss the efficiency of the approach and the scalability of its implementation with regard to the future development of quantum hardware. © 2006 IEEE.

关键词： Networks (circuits)

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Unconditional Privacy over Channels which Cannot Convey quantum Information

引用

Physical Review Letters 2008年第11期100卷 110502-110502页

作者： K. Horodecki M. Horodecki P. Horodecki D. Leung J. Oppenheim Department of Math Physics and Computer Science University of Gdańsk Gdańsk Poland National Quantum Information Centre of Gdańsk 81-824 Sopot Poland Institute of Theoretical Physics and Astrophysics University of Gdańsk Gdańsk Poland Faculty of Applied Physics and Math Technical University of Gdańsk Gdańsk Poland Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L1N8 Canada Department of Applied Mathematics and Theoretical Physics University of Cambridge United Kingdom

quantum cryptography enables one to verify that the state of the quantum system has not been tampered with and thus one can obtain privacy regardless of the power of the eavesdropper. All previous protocols relied on the ability to faithfully send quantum states or equivalently to share pure entanglement. Here we show this need not be the case—one can obtain verifiable privacy even through some channels which cannot be used to reliably send quantum states.

关键词： quantum cryptography

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