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Theoretical Aspects of Software Engineering (TASE)

作者： Xiaoxiao Yang Zhenhua Duan Institute of Computing Theory & Technology and ISN Laboratory Xidian University Xi'an China State Key Laboratory of Computer Science Institute of Software Chinese Academy and Sciences China

In this paper, we investigate the axiomatic system of Modeling Simulation and Verification Language (MSVL). To this end, a set of state axioms and state inference rules is given. They are useful to deduce a program into its normal form. Further, a propositional projection temporal logic is used as assertion language to describe the required property of a program. Moreover, to deduce a program over an interval, a set of rules in terms of triple like Hoare logic is formalized. These rules enable us to deduce a program in its normal form at the current state to the next one and to verify safety, liveness properties over an interval.

关键词： Semantics Writing Logic programming Computational modeling Laboratories Software

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Online Markov decision processes under bandit feedback 10

Online Markov decision processes under bandit feedback

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Proceedings of the 24th International Conference on Neural Information Processing Systems - Volume 2

作者： Gergely Neu András György Csaba Szepesvári András Antos Department of Computer Science and Information Theory Budapest University of Technology and Economics Hungary Machine Learning Research Group MTA SZTAKI Institute for Computer Science and Control Hungary Department of Computing Science University of Alberta Canada Machine Learning Research Group MTA SZTAKI Institute for Computer Science and Control Hungary

We consider online learning in finite stochastic Markovian environments where in each time step a new reward function is chosen by an oblivious adversary. The goal of the learning agent is to compete with the best stationary policy in terms of the total reward received. In each time step the agent observes the current state and the reward associated with the last transition, however, the agent does not observe the rewards associated with other state-action pairs. The agent is assumed to know the transition probabilities. The state of the art result for this setting is a no-regret algorithm. In this paper we propose a new learning algorithm and, assuming that stationary policies mix uniformly fast, we show that after T time steps, the expected regret of the new algorithm is O (T2/3 (ln T)1/3), giving the first rigorously proved regret bound for the problem.

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Passive decoy-state quantum key distribution with practical light sources

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Physical Review A 2010年第2期81卷 022310-022310页

作者： Marcos Curty Xiongfeng Ma Bing Qi Tobias Moroder ETSI Telecomunicación Department of Signal Theory and Communications University of Vigo Campus Universitario E-36310 Vigo (Pontevedra) Spain Institute for Quantum Computing & Department of Physics and Astronomy University of Waterloo N2L 3G1 Waterloo Ontario Canada Center for Quantum Information and Quantum Control Department of Physics and Department of Electrical & Computer Engineering University of Toronto M5S 3G4 Toronto Ontario Canada Quantum Information Theory Group Institute of Theoretical Physics I University of Erlangen-Nürnberg D-91058 Erlangen Germany Max Planck Institute for the Science of Light D-91058 Erlangen Germany

Decoy states have been proven to be a very useful method for significantly enhancing the performance of quantum key distribution systems with practical light sources. Although active modulation of the intensity of the laser pulses is an effective way of preparing decoy states in principle, in practice passive preparation might be desirable in some scenarios. Typical passive schemes involve parametric down-conversion. More recently, it has been shown that phase-randomized weak coherent pulses (WCP) can also be used for the same purpose [M. Curty et al., Opt. Lett. 34, 3238 (2009).] This proposal requires only linear optics together with a simple threshold photon detector, which shows the practical feasibility of the method. Most importantly, the resulting secret key rate is comparable to the one delivered by an active decoy-state setup with an infinite number of decoy settings. In this article we extend these results, now showing specifically the analysis for other practical scenarios with different light sources and photodetectors. In particular, we consider sources emitting thermal states, phase-randomized WCP, and strong coherent light in combination with several types of photodetectors, like, for instance, threshold photon detectors, photon number resolving detectors, and classical photodetectors. Our analysis includes as well the effect that detection inefficiencies and noise in the form of dark counts shown by current threshold detectors might have on the final secret key rate. Moreover, we provide estimations on the effects that statistical fluctuations due to a finite data size can have in practical implementations.

关键词： Photodetectors

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Robustness of ethnocentrism to changes in interpersonal interactions

Robustness of ethnocentrism to changes in interpersonal inte...

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2010 AAAI Fall Symposium

作者： Kaznatcheev, Artem School of Computer Science Department of Psychology McGill University 3600 University Street Montreal QC H3A 2T8 Canada Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo 200 University Avenue West Waterloo ON N2L 3G1 Canada

ISBN: (纸本)9781577354857

We use the methods of evolutionary game theory and computational modelling to examine the evolution of ethnocentrism. We show that ethnocentrism evolves in a spatially structured population not only under prisoner's dilemma interactions, but also hawk-dove, assurance, harmony, and leader games. In the case of harmony, ethnocentrism evolves even when defection is irrational. This suggests that the pressure of competing for a common resource (in our model: free space) can produce irrational hostility between groups. The minimal cognitive assumptions in our model also suggest that the ethnocentrism observed in humans and elsewhere in nature has an evolutionary basis that is robust over changes in interaction types. Copyright © 2010, Association for the Advancement of Artificial Intelligence. All rights reserved.

关键词： Game theory

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Passive sources for the Bennett-Brassard 1984 quantum-key-distribution protocol with practical signals

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Physical Review A 2010年第5期82卷 052325-052325页

作者： Marcos Curty Xiongfeng Ma Hoi-Kwong Lo Norbert Lütkenhaus ETSI Telecomunicación Department of Signal Theory and Communications University of Vigo Campus Universitario E-36310 Vigo Pontevedra Spain Institute for Quantum Computing & Department of Physics and Astronomy University of Waterloo Waterloo Ontario N2L 3G1 Canada Center for Quantum Information and Quantum Control Department of Physics and Department of Electrical & Computer Engineering University of Toronto Toronto Ontario M5S 3G4 Canada

Most experimental realizations of quantum key distribution are based on the Bennett-Brassard 1984 (the so-called BB84) protocol. In a typical optical implementation of this scheme, the sender uses an active source to produce the required BB84 signal states. While active state preparation of BB84 signals is a simple and elegant solution in principle, in practice passive state preparation might be desirable in some scenarios, for instance, in those experimental setups operating at high transmission rates. Passive schemes might also be more robust against side-channel attacks than active sources. Typical passive devices involve parametric down-conversion. In this paper, we show that both coherent light and practical single-photon sources are also suitable for passive generation of BB84 signal states. Our method does not require any externally driven element, but only linear optical components and photodetectors. In the case of coherent light, the resulting key rate is similar to the one delivered by an active source. When the sender uses practical single-photon sources, however, the distance covered by a passive transmitter might be longer than that of an active configuration.

关键词： Side channel attack

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quantum State Reduction for Universal Measurement Based Computation

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Physical Review Letters 2010年第2期105卷 020502-020502页

作者： Xie Chen Runyao Duan Zhengfeng Ji Bei Zeng Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts USA Centre for Quantum Computation and Intelligent Systems (QCIS) Faculty of Engineering and Information Technology University of Technology Sydney NSW Australia Department of Computer Science and Technology Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing China Perimeter Institute for Theoretical Physics Waterloo Ontario Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing China Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada Department of Combinatorics and Optimization University of Waterloo Waterloo Ontario Canada

Measurement based quantum computation, which requires only single particle measurements on a universal resource state to achieve the full power of quantum computing, has been recognized as one of the most promising models for the physical realization of quantum computers. Despite considerable progress in the past decade, it remains a great challenge to search for new universal resource states with naturally occurring Hamiltonians and to better understand the entanglement structure of these kinds of states. Here we show that most of the resource states currently known can be reduced to the cluster state, the first known universal resource state, via adaptive local measurements at a constant cost. This new quantum state reduction scheme provides simpler proofs of universality of resource states and opens up plenty of space to the search of new resource states.

关键词： quantum computers

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Multi-error-correcting amplitude damping codes

Multi-error-correcting amplitude damping codes

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IEEE International Symposium on Information theory

作者： Runyao Duan Markus Grassl Zhengfeng Ji Bei Zeng State Key Laboratory of Intelligent Technology and Systems Tsinghua National Laboratory for Information Science and Technology Department of Computer Science and Technology Tsinghua University Beijing China Centre for Quantum Computation and Intelligent Systems (QCIS) Faculty of Engineering and Information Technology University of Technology Sydney NSW Australia Centre for Quantum Technologies National University of Singapore Singapore Perimeter Institute of Theoretical Physics Waterloo ONT Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy and Sciences Beijing China Institute for Quantum Computing and the Department of Combinatorics and Optimization University of Waterloo Waterloo ONT Canada

ISBN: (纸本)9781424478903

We construct new families of multi-error-correcting quantum codes for the amplitude damping channel. Our key observation is that, with proper encoding, two uses of the amplitude damping channel simulate a quantum erasure channel. This allows us to use concatenated codes with quantum erasure-correcting codes as outer codes for correcting multiple amplitude damping errors. Our new codes are degenerate stabilizer codes and have parameters which are better than the amplitude damping codes obtained by any previously known construction.

关键词： Damping quantum mechanics quantum computing Error correction codes Noise level Laboratories Phase noise Physics computing Intelligent systems computer science

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First-principles study of Fe/MgO based magnetic tunnel junctions with Mg interlayers

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Physical Review B 2010年第5期82卷 054405-054405页

作者： Yan Wang Jia Zhang X.-G. Zhang Hai-Ping Cheng X. F. Han Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics and Quantum Theory Project University of Florida Gainesville Florida 32611 USA Center for Nanophase Materials Sciences and Computer Science and Mathematics Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831-6164 USA

-Fe(001)/Mg/MgO/Fe- and -Fe(001)/Mg/MgO/Mg/Fe- magnetic tunnel junctions (MTJs) with Mg interlayers are studied by first-principles calculations. We find that the Mg interlayer is able to preserve the preferential transmission of the majority-spin states with Δ1 symmetry, which dominates the spin-dependent electron transport in MTJs with MgO barrier. A monoatomic layer of Mg at the electrode/barrier interface does not decrease the tunneling magnetoresistance (TMR) ratio nearly as much as a similar layer of iron oxide. We also find that at a certain Mg thickness the TMR is strongly influenced by resonant tunneling in the minority-spin channel. These resonances are due to the coupling between the quantum-well states within the Mg interlayer to the interfacial resonance states on the Fe/Mg interface. The calculated results are used to explain experimental measurements of MTJs with Mg interlayers.

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quantum-capacity-approaching codes for the detected-jump channel

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Physical Review A 2010年第6期82卷 062324-062324页

作者： Markus Grassl Zhengfeng Ji Zhaohui Wei Bei Zeng Centre for Quantum Technologies National University of Singapore Singapore 117543 Singapore Perimeter Institute for Theoretical Physics Waterloo Ontario N2L 2Y5 Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing 100190 China Department of Mathematics and Statistics University of Guelph Guelph Ontario N1G 2W1 Canada Institute for Quantum Computing and Department of Combinatorics and Optimization University of Waterloo Waterloo Ontario N2L 3G1 Canada

The quantum-channel capacity gives the ultimate limit for the rate at which quantum data can be reliably transmitted through a noisy quantum channel. Degradable quantum channels are among the few channels whose quantum capacities are known. Given the quantum capacity of a degradable channel, it remains challenging to find a practical coding scheme which approaches capacity. Here we discuss code designs for the detected-jump channel, a degradable channel with practical relevance describing the physics of spontaneous decay of atoms with detected photon emission. We show that this channel can be used to simulate a binary classical channel with both erasures and bit flips. The capacity of the simulated classical channel gives a lower bound on the quantum capacity of the detected-jump channel. When the jump probability is small, it almost equals the quantum capacity. Hence using a classical capacity-approaching code for the simulated classical channel yields a quantum code which approaches the quantum capacity of the detected-jump channel.

关键词： quantum capacity approaching jump spontaneous decay quanta labeling scheme Codes quantum dense coding ultimate limits

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Entanglement verification with realistic measurement devices via squashing operations

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Physical Review A 2010年第5期81卷 052342-052342页

作者： Tobias Moroder Otfried Gühne Normand Beaudry Marco Piani Norbert Lütkenhaus Quantum Information Theory Group Institute of Theoretical Physics I University Erlangen-Nuremberg Staudtstraße 7/B2 D-91058 Erlangen Germany Max Planck Institute for the Science of Light Günther-Scharowsky-Straße 1/24 D-91058 Erlangen Germany Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo 200 University Avenue West N2L 3G1 Waterloo Ontario Canada Institut für Quantenoptik und Quanteninformation Österreichische Akademie der Wissenschaften Technikerstraße 21A A-6020 Innsbruck Austria Institut für Theoretische Physik Universität Innsbruck Technikerstraße 25 A-6020 Innsbruck Austria

Many protocols and experiments in quantum information science are described in terms of simple measurements on qubits. However in a real implementation the exact description is more difficult and more complicated observables are used. The question arises whether a claim of entanglement in the simplified description still holds, if the difference between the realistic and simplified models is taken into account. We show that a positive entanglement statement remains valid if a certain positive linear map connecting the two descriptions—a so-called squashing operation—exists; then lower bounds on the amount of entanglement are also possible. We apply our results to polarization measurements of photons using only threshold detectors, and derive procedures under which multiphoton events can be neglected.

关键词： quantum optics

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