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Randomness expansion with a one-sided trusted device

Physical Review A 2015年第5期91卷 052308-052308页

作者： Hong Wang Kai Chen Ming Gao Zhi Ma Weilong Wang Chaobo Li Chuangui Ma State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou 450002 China Zhengzhou Information Science and Technology Institute Zhengzhou 450002 China National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei 230026 P.R. China CAS Excellence Innovation Center Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 China

We study a semi-device-independent (SDI) randomness expansion protocol with a trusted source or detector. It is not difficult to characterize the source or the detector when their dimensions are limited in the SDI scenario. By adding the reasonable assumption, our protocol offers higher min-entropy and, thus, can be used to certify more randomness than the standard SDI protocol of H.-W. Li et al. [Phys. Rev. A 84, 034301 (2011)]. Moreover, randomness expansion can be realized with a lower detection efficiency (about 85.4%) in the trusted source case than the standard one (about 93.4%). Meanwhile, this advantage is robust against parameter deviations of the source. But on the other hand, the sharp measurement cannot improve the performance much in this case. So, there is no need to characterize the measurement accurately. Furthermore, an analytical formula describing the relationship between the dimension witness value and the min-entropy of the output string is derived directly.

关键词： quantum measurement DETECTORS ENTROPY (Information theory) PERFORMANCE evaluation quantum information theory

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Effect of source tampering in the security of quantum cryptography

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Physical Review A 2015年第2期92卷 022304-022304页

作者： Shi-Hai Sun Feihu Xu Mu-Sheng Jiang Xiang-Chun Ma Hoi-Kwong Lo Lin-Mei Liang College of Science National University of Defense Technology Changsha 410073 China Center for Quantum Information and Quantum Control Department of Electrical and Computer Engineering and Department of Physics University of Toronto Toronto Ontario M5S 3G4 Canada Research Laboratory of Electronics Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA State Key Laboratory of High Performance Computing National University of Defense Technology Changsha 410073 China

The security of source has become an increasingly important issue in quantum cryptography. Based on the framework of measurement-device-independent quantum key distribution (MDI-QKD), the source becomes the only region exploitable by a potential eavesdropper (Eve). Phase randomization is a cornerstone assumption in most discrete-variable (DV) quantum communication protocols (e.g., QKD, quantum coin tossing, weak-coherent-state blind quantum computing, and so on), and the violation of such an assumption is thus fatal to the security of those protocols. In this paper, we show a simple quantum hacking strategy, with commercial and homemade pulsed lasers, by Eve that allows her to actively tamper with the source and violate such an assumption, without leaving a trace afterwards. Furthermore, our attack may also be valid for continuous-variable (CV) QKD, which is another main class of QKD protocol, since, excepting the phase random assumption, other parameters (e.g., intensity) could also be changed, which directly determine the security of CV-QKD.

关键词： quantum cryptography quantum communication quantum coherence RANDOMIZATION (Statistics) quantum computing

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OpenFermion: The electronic structure package for quantum computers

arXiv

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arXiv 2017年

作者： McClean, Jarrod R. Sung, Kevin J. Kivlichan, Ian D. Cao, Yudong Dai, Chengyu Schuyler Fried, E. Gidney, Craig Gimby, Brendan Gokhale, Pranav Häner, Thomas Hardikar, Tarini Havlíček, Vojtěch Higgott, Oscar Huang, Cupjin Izaac, Josh Jiang, Zhang Liu, Xinle McArdle, Sam Neeley, Matthew O'Brien, Thomas O'Gorman, Bryan Ozfidan, Isil Radin, Maxwell D. Romero, Jhonathan Rubin, Nicholas Sawaya, Nicolas P.D. Setia, Kanav Sim, Sukin Steiger, Damian S. Steudtner, Mark Sun, Qiming Sun, Wei Wang, Daochen Zhang, Fang Babbush, Ryan Google Inc. VeniceCA90291 United States Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States Department of Physics Harvard University CambridgeMA02138 United States Department of Chemistry and Chemical Biology Harvard University CambridgeMA02138 United States Zapata Computing Inc. Cambridge02138 United States Department of Physics University of Michigan Ann ArborMI48109 United States Rigetti Computing BerkeleyCA94710 United States Google Inc. Santa BarbaraCA93117 Department of Computer Science University of Chicago ChicagoIL60637 United States Theoretische Physik ETH Zurich Zurich8093 Switzerland Department of Physics Dartmouth College HanoverNH03755 United States Department of Computer Science Oxford University OxfordOX1 3QD United Kingdom Department of Physics and Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom Xanadu 372 Richmond St W TorontoM5V 1X6 Canada QuAIL NASA Ames Research Center Moffett FieldCA94035 Google Inc. Mountain ViewCA94043 United States Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom Instituut-Lorentz Universiteit Leiden Leiden2300 RA Netherlands BQIC University of California BerkeleyCA94720 United States D-Wave Systems Inc. BurnabyBC Canada Materials Department University of California Santa Barbara Santa BarbaraCA93106 United States QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Division of Chemistry and Chemical Engineering California Institute of Technology PasadenaCA91125 United States Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States

quantum simulation of chemistry and materials is predicted to be an important application for both near-term and fault-tolerant quantum devices. However, at present, developing and studying algorithms for these problems can be difficult due to the prohibitive amount of domain knowledge required in both the area of chemistry and quantum algorithms. To help bridge this gap and open the field to more researchers, we have developed the OpenFermion software package (***). OpenFermion is an open-source software library written largely in Python under an Apache 2.0 license, aimed at enabling the simulation of fermionic and bosonic models and quantum chemistry problems on quantum hardware. Beginning with an interface to common electronic structure packages, it simplifies the translation between a molecular specification and a quantum circuit for solving or studying the electronic structure problem on a quantum computer, minimizing the amount of domain expertise required to enter the field. The package is designed to be extensible and robust, maintaining high software standards in documentation and testing. This release paper outlines the key motivations behind design choices in OpenFermion and discusses some basic OpenFermion functionality which we believe will aid the community in the development of better quantum algorithms and tools for this exciting area of research. Copyright © 2017, The Authors. All rights reserved.

关键词： Electronic structure

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Gravitational wave astronomy: the current status

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Science China(Physics,Mechanics & Astronomy) 2015年第12期58卷 3-43页

作者： BLAIR David JU Li ZHAO ChunNong WEN LinQing CHU Qi FANG Qi CAI RongGen GAO JiangRui LIN XueChun LIU Dong WU Ling-An ZHU ZongHong REITZE David H. ARAI Koji ZHANG Fan FLAMINIO Raffaele ZHU XingJiang HOBBS George MANCHESTER Richard N. SHANNON Ryan M. BACCIGALUPI Carlo GAO Wei XU Peng BIAN Xing CAO ZhouJian CHANG ZiJing DONG Peng GONG XueFei HUANG ShuangLin JU Peng LUO ZiRen QIANG Li'E TANG WenLin WAN XiaoYun WANG Yue XU ShengNian ZANG YunLong ZHANG HaiPeng LAU Yun-Kau NI Wei-Tou School of Physics The University of Western Australia State Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences The School of Physics & Electronic Engineering Shanxi University Laboratory of All-Solid-State Light Sources Institute of Semiconductors Chinese Academy of Science State Key Laboratroy of Modern Optical Instrumentation Department of Optical Engineering Zhejiang University Laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Gravitational Wave and Cosmology Laboratory Department of Astronomy Beijing Normal University LIGO Laboratory California Institute of Technology Department of Physics University of Florida Department of Physics West Virginia University National Astronomical Observatory of Japan CSIRO Astronomy and Space Science International Centre for Radio Astronomy Research Curtin University SISSA Astrophysics Sector Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences University of Chinese Academy of Sciences Morningside Center of Mathematics Chinese Academy of Sciences State Key Laboratory of Scientific and Engineering Computing Academy of Mathematics and Systems ScienceChinese Academy of Sciences Department of Mathematics Henan University Department of Mathematics Capital Normal University Department of Geophysics College of the Geology Engineering and Geomatics Chang'an University QUEST Centre of Quantum Engineering and Space-Time Research Leibniz Universitt Hannover Max-Planck-Institut für Gravitationsphysik(Albert Einstein Institut) Aerospace Flight Dynamics Laboratory Beijing Aerospace Control Center Qian Xuesen Laboratory of Launch Vehicle Technology Center for Gravitation and Cosmology Department of Physics Tsing Hua University

In the centenary year of Einstein's General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein's first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan,which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1–5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.

关键词： gravitational waves ground based detectors pulsar timing spaced based detectors CMB

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Dynamics of parametric fluctuations induced by quasiparticle tunneling in superconducting flux qubits

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Physical Review B 2015年第19期91卷 195434-195434页

作者： M. Bal M. H. Ansari J.-L. Orgiazzi R. M. Lutchyn A. Lupascu Institute for Quantum Computing Department of Physics and Astronomy and Waterloo Institute for Nanotechnology University of Waterloo Waterloo ON Canada N2L 3G1 TUBITAK Marmara Research Centre Materials Institute P.O. Box 21 41470 Gebze Kocaeli Turkey Kavli Institute of Nanoscience Delft University of Technology P.O. Box 5046 2600 GA Delft The Netherlands Institute for Quantum Computing Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology University of Waterloo Waterloo ON Canada N2L 3G1 Station Q Microsoft Research Santa Barbara California 93106-6105 USA

We present experiments on the dynamics of a two-state parametric fluctuator in a superconducting flux qubit. In spectroscopic measurements, the fluctuator manifests itself as a doublet line. When the qubit is excited in resonance with one of the two doublet lines, the correlation of readout results exhibits an exponential time decay which provides a measure of the fluctuator transition rate. The rate increases with temperature in the interval 40 to 158 mK. Based on the magnitude of the transition rate and the doublet line splitting, we conclude that the fluctuation is induced by quasiparticle tunneling. These results demonstrate the importance of considering quasiparticles as a source of decoherence in flux qubits.

关键词： QUBITS FLUCTUATIONS (Physics) TUNNELING (Physics) SUPERCONDUCTING thin films QUASIPARTICLES (Physics) DECOHERENCE (quantum mechanics) PARAMETRIC equations

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Experimental quantum key distribution with source flaws

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Physical Review A 2015年第3期92卷 032305-032305页

作者： Feihu Xu Kejin Wei Shihan Sajeed Sarah Kaiser Shihai Sun Zhiyuan Tang Li Qian Vadim Makarov Hoi-Kwong Lo Centre for Quantum Information and Quantum Control (CQIQC) Department of Electrical & Computer Engineering and Department of Physics University of Toronto Toronto Ontario M5S 3G4 Canada School of Science and State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing 100876 China Institute for Quantum Computing (IQC) University of Waterloo Waterloo Ontario N2L 3G1 Canada Department of Electrical and Computer Engineering University of Waterloo Waterloo Ontario N2L 3G1 Canada Department of Physics and Astronomy University of Waterloo Waterloo Ontario N2L 3G1 Canada College of Science National University of Defense Technology Changsha 410073 China

Decoy-state quantum key distribution (QKD) is a standard technique in current quantum cryptographic implementations. Unfortunately, existing experiments have two important drawbacks: the state preparation is assumed to be perfect without errors and the employed security proofs do not fully consider the finite-key effects for general attacks. These two drawbacks mean that existing experiments are not guaranteed to be proven to be secure in practice. Here, we perform an experiment that shows secure QKD with imperfect state preparations over long distances and achieves rigorous finite-key security bounds for decoy-state QKD against coherent attacks in the universally composable framework. We quantify the source flaws experimentally and demonstrate a QKD implementation that is tolerant to channel loss despite the source flaws. Our implementation considers more real-world problems than most previous experiments, and our theory can be applied to general discrete-variable QKD systems. These features constitute a step towards secure QKD with imperfect devices.

关键词： quantum states quantum theory quantum entanglement quantum cryptography quantum computing

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Laser Damage Helps the Eavesdropper in quantum Cryptography

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Physical Review Letters 2014年第7期112卷 070503-070503页

作者： Audun Nystad Bugge Sebastien Sauge Aina Mardhiyah M. Ghazali Johannes Skaar Lars Lydersen Vadim Makarov Department of Electronics and Telecommunications Norwegian University of Science and Technology NO-7491 Trondheim Norway School of Information and Communication Technology Royal Institute of Technology (KTH) Electrum 229 SE-16440 Kista Sweden Department of Science in Engineering Faculty of Engineering International Islamic University Malaysia P.O. Box 10 50728 Kuala Lumpur Malaysia Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3G1 Canada

We propose a class of attacks on quantum key distribution (QKD) systems where an eavesdropper actively engineers new loopholes by using damaging laser illumination to permanently change properties of system components. This can turn a perfect QKD system into a completely insecure system. A proof-of-principle experiment performed on an avalanche photodiode-based detector shows that laser damage can be used to create loopholes. After ∼1 W illumination, the detectors’ dark count rate reduces 2–5 times, permanently improving single-photon counting performance. After ∼1.5 W, the detectors switch permanently into the linear photodetection mode and become completely insecure for QKD applications.

关键词： LASER damage quantum cryptography PHOTODIODES SINGLE-photon emission computed tomography SINGLE photon generation

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quantum Nondemolition Detection of a Propagating Microwave Photon

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Physical Review Letters 2014年第9期112卷 093601-093601页

作者： Sankar R. Sathyamoorthy L. Tornberg Anton F. Kockum Ben Q. Baragiola Joshua Combes C. M. Wilson Thomas M. Stace G. Johansson Department of Microtechnology and Nanoscience MC2 Chalmers University of Technology S-41296 Gothenburg Sweden Center for Quantum Information and Control University of New Mexico Albuquerque New Mexico 87131-0001 USA Institute for Quantum Computing and Electrical and Computer Engineering Department University of Waterloo Waterloo N2 L 3G1 Canada Centre for Engineered Quantum Systems School of Physical Sciences University of Queensland Saint Lucia Queensland 4072 Australia

The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realizing such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon interactions in a waveguide have recently been demonstrated. Here we show how this type of interaction can be used to realize a quantum nondemolition measurement of a single propagating microwave photon. The scheme we propose uses a chain of solid-state three-level systems (transmons) cascaded through circulators which suppress photon backscattering. Our theoretical analysis shows that microwave-photon detection with fidelity around 90% can be realized with existing technologies.

关键词： MICROWAVE photonics RESEARCH quantum mechanics quantum information science PHOTON-photon interactions WAVEGUIDES PHOTON scattering BACKSCATTERING

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Quasiholes of 13 and 73 quantum Hall states: Size estimates via exact diagonalization and density-matrix renormalization group

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Physical Review B 2014年第11期89卷 115124-115124页

作者： Sonika Johri Z. Papić R. N. Bhatt P. Schmitteckert Department of Electrical Engineering Princeton University Princeton New Jersey 08544 USA Perimeter Institute for Theoretical Physics Waterloo ON N2L 2Y5 Canada Institute for Quantum Computing Waterloo ON N2L 3G1 Canada Institute for Advanced Study Princeton New Jersey 08540 USA Institute of Nanotechnology Karlsruhe Institute of Technology 76344 Eggenstein-Leopoldshafen Germany

We determine the size of the elementary quasihole in ν=1/3 and ν=7/3 quantum Hall states via exact-diagonalization and density-matrix renormalization group calculations on the sphere and cylinder, using a variety of short- and long-range pinning potentials. The size of the quasihole at filling factor ν=1/3 is estimated to be ≈4ℓB, and that of ν=7/3 is ≈7ℓB, where ℓB is the magnetic length. In contrast, the size of the Laughlin quasihole, expected to capture the basic physics in these two states, is around ≈2.5ℓB. Our work supports the earlier findings that the quasihole in the first excited Landau level is significantly larger than in the lowest Landau level.

关键词： quantum Hall effect DENSITY matrices RENORMALIZATION group LANDAU levels WAVE functions

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Observation of tunnel magnetoresistance in a superconducting junction with Zeeman-split energy bands

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Physical Review B 2013年第16期88卷 161105(R)-161105(R)页

作者： Bin Li Guo-Xing Miao Jagadeesh S. Moodera Francis Bitter Magnet Laboratory Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Institute for Quantum Computing and Department of Electrical and Computer Engineering University of Waterloo Waterloo Ontario Canada N2L3G1 Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

The change of the quasiparticle density of states in a superconductor due to the Zeeman splitting can lead to highly responsive spintronic devices. This is demonstrated here in the magnetotunneling studies of a supercondcutor/insulator/ferromagnet tunnel junction. A tunnel magnetoresistance (TMR) as large as 36% is obtained, resulting from the conductance variation due to spin-split quasiparticle tunneling, and only occurs in the superconducting state. Our results show that in addition to the naturally existent spin imbalance in ferromagnets (upon which conventional TMR is obtained), we can manipulate tunnel conductance by tailoring spin dependent density of states with interfacial exchange fields, and even with a tunnel junction with both superconducting electrodes.

关键词： MAGNETORESISTANCE SUPERCONDUCTING junction devices SPINTRONICS ENERGY bands ZEEMAN effect

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