检索结果-内蒙古大学图书馆

Complete characterization of the ground-space structure of two-body frustration-free Hamiltonians for qubits

Physical Review A 2011年第4期84卷 042338-042338页

作者： Zhengfeng Ji Zhaohui Wei Bei Zeng Perimeter Institute for Theoretical Physics 31 Caroline Street North Waterloo Ontario N2L 2Y5 Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing China Centre for Quantum Technologies National University of Singapore Singapore 117543 Singapore Department of Mathematics & Statistics University of Guelph Guelph Ontario N1G 2W1 Canada Institute for Quantum Computing University of Waterloo Waterloo Ontario N2L 3G1 Canada

The problem of finding the ground state of a frustration-free Hamiltonian carrying only two-body interactions between qubits is known to be solvable in polynomial time. It is also shown recently that, for any such Hamiltonian, there is always a ground state that is a product of single- or two-qubit states. However, it remains unclear whether the whole ground space is of any succinct structure. Here, we give a complete characterization of the ground space of any two-body frustration-free Hamiltonian of qubits. Namely, it is a span of tree tensor network states of the same tree structure. This characterization allows us to show that the problem of determining the ground-state degeneracy is as hard as, but no harder than, its classical analog.

关键词： HAMILTONIAN systems HAMILTON-Jacobi equations OPTICS PHYSICS POLYNOMIALS

来源：评论

学校读者我要写书评

暂无评论

All Nonclassical Correlations Can Be Activated into Distillable Entanglement

引用

Physical Review Letters 2011年第22期106卷 220403-220403页

作者： Marco Piani Sevag Gharibian Gerardo Adesso John Calsamiglia Paweł Horodecki Andreas Winter Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo Waterloo N2L 3G1 Canada Institute for Quantum Computing and School of Computer Science University of Waterloo Waterloo N2L 3G1 Canada School of Mathematical Sciences University of Nottingham University Park Nottingham NG7 2RD United Kingdom Física Teòrica: Informació i Fenòmens Quàntics Universitat Autònoma de Barcelona 08193 Bellaterra Spain Faculty of Applied Physics and Mathematics Technical University of Gdańsk 80-952 Gdańsk Poland National Quantum Information Centre of Gdańsk 81-824 Sopot Poland Department of Mathematics University of Bristol Bristol BS8 1TW United Kingdom Centre for Quantum Technologies National University of Singapore Singapore 117542

We devise a protocol in which general nonclassical multipartite correlations produce a physically relevant effect, leading to the creation of bipartite entanglement. In particular, we show that the relative entropy of quantumness, which measures all nonclassical correlations among subsystems of a quantum system, is equivalent to and can be operationally interpreted as the minimum distillable entanglement generated between the system and local ancillae in our protocol. We emphasize the key role of state mixedness in maximizing nonclassicality: Mixed entangled states can be arbitrarily more nonclassical than separable and pure entangled states.

关键词： quantum optics

来源：评论

学校读者我要写书评

暂无评论

Entanglement can Completely Defeat quantum Noise

引用

Physical Review Letters 2011年第25期107卷 250504-250504页

作者： Jianxin Chen Toby S. Cubitt Aram W. Harrow Graeme Smith Department of Mathematics & Statistics U. of Guelph Guelph Ontario Canada Institute for Quantum Computing U. of Waterloo Waterloo Ontario Canada Departamento de Análisis Matemático U. Complutense de Madrid Plaza de Ciencias 3 28040 Madrid Spain Department of Computer Science & Engineering U. of Washington Seattle Washington 98195 USA IBM T.J. Watson Research Center Yorktown Heights New York 10598 USA

We describe two quantum channels that individually cannot send any classical information without some chance of decoding error. But together a single use of each channel can send quantum information perfectly reliably. This proves that the zero-error classical capacity exhibits superactivation, the extreme form of the superadditivity phenomenon in which entangled inputs allow communication over zero-capacity channels. But our result is stronger still, as it even allows zero-error quantum communication when the two channels are combined. Thus our result shows a new remarkable way in which entanglement across two systems can be used to resist noise, in this case perfectly. We also show a new form of superactivation by entanglement shared between sender and receiver.

关键词： NOISE quantum communication ERROR OPTICAL communications quantum theory

来源：评论

学校读者我要写书评

暂无评论

QIP = PSPACE 10

QIP = PSPACE

引用

42nd ACM Symposium on theory of computing, STOC 2010

作者： Jain, Rahul Ji, Zhengfeng Upadhyay, Sarvagya Watrous, John Department of Computer Science Centre for Quantum Technologies National University of Singapore Singapore Perimeter Institute for Theoretical Physics Waterloo ON Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing China Institute for Quantum Computing School of Computer Science University of Waterloo Waterloo ON Canada

ISBN: (纸本)9781605588179

We prove that the complexity class QIP, which consists of all problems having quantum interactive proof systems, is contained in PSPACE. This containment is proved by applying a parallelized form of the matrix multiplicative weights update method to a class of semidefinite programs that captures the computational power of quantum interactive proofs. As the containment of PSPACE in QIP follows immediately from the well-known equality IP = PSPACE, the equality QIP = PSPACE follows. © 2010 ACM.

关键词： quantum computers

来源：评论

学校读者我要写书评

暂无评论

Axiomatic temporal logic programs verification

Axiomatic temporal logic programs verification

引用

2010 4th International Symposium on Theoretical Aspects of Software Engineering, TASE 2010

作者： Yang, Xiaoxiao Duan, Zhenhua Institute of Computing Theory and Technology ISN Laboratory Xidian University Xi'an710071 China State Key Laboratory of Computer Science Institute of Software Chinese Academy of Science China

ISBN: (纸本)9780769541488

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. © 2010 IEEE.

关键词： Semantics

来源：评论

学校读者我要写书评

暂无评论

Entanglement in channel discrimination with restricted measurements

引用

Physical Review A 2010年第3期82卷 032302-032302页

作者： William Matthews Marco Piani John Watrous Institute for Quantum Computing and School of Computer Science University of Waterloo Waterloo Ontario Canada

We study the power of measurements implementable with local quantum operations and classical communication (LOCC) measurements in the setting of quantum channel discrimination. More precisely, we consider discrimination procedures that attempt to identify an unknown channel, chosen uniformly from two known alternatives, that take the following form: (i) the input to the unknown channel is prepared in a possibly entangled state with an ancillary system, (ii) the unknown channel is applied to the input system, and (iii) an LOCC measurement is performed on the output and ancillary systems, resulting in a guess for which of the two channels was given. The restriction of the measurement in such a procedure to be an LOCC measurement is of interest because it isolates the entanglement in the initial input-ancillary systems as a resource in the setting of channel discrimination. We prove that there exist channel discrimination problems for which restricted procedures of this sort can be at either of the two extremes: they may be optimal within the set of all discrimination procedures (and simultaneously outperform all strategies that make no use of entanglement), or they may be no better than unentangled strategies (and simultaneously suboptimal within the set of all discrimination procedures).

关键词： quantum entanglement

来源：评论

学校读者我要写书评

暂无评论

Online Markov decision processes under bandit feedback

Online Markov decision processes under bandit feedback

引用

24th Annual Conference on Neural Information Processing Systems 2010, NIPS 2010

作者： Neu, Gergely György, András Szepesvári, Csaba Antos, András 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

ISBN: (纸本)9781617823800

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.

关键词： Learning algorithms

来源：评论

学校读者我要写书评

暂无评论

The online loop-free stochastic shortest-path problem

The online loop-free stochastic shortest-path problem

引用

23rd Conference on Learning theory, COLT 2010

作者： Neu, Gergely György, András Szepesvári, Csaba Department of Computer Science and Information Theory Budapest University of Technology and Economics Hungary Machine Learning Research Group Computer and Automation Research Institute Hungarian Academy of Sciences Hungary Department of Computing Science University of Alberta Canada

ISBN: (纸本)9780982252925

We consider a stochastic extension of the loop-free shortest path problem with adversarial rewards. In this episodic Markov decision problem an agent traverses through an acyclic graph with random transitions: at each step of an episode the agent chooses an action, receives some reward, and arrives at a random next state, where the reward and the distribution of the next state depend on the actual state and the chosen action. We consider the bandit situation when only the reward of the just visited state-action pair is revealed to the agent. For this problem we develop algorithms that perform asymptotically as well as the best stationary policy in hindsight. Assuming that all states are reachable with probability α > 0 under all policies, we give an algorithm and prove that its regret is 0(L2 √T\A\/α), where T is the number of episodes, A denotes the (finite) set of actions, and L is the length of the longest path in the graph. Variants of the algorithm are given that improve the dependence on the transition probabilities under specific conditions. The results are also extended to variations of the problem, including the case when the agent competes with time varying policies.

关键词： Stochastic systems

来源：评论

学校读者我要写书评

暂无评论

quantum benchmarks for the storage or transmission of quantum light from minimal resources

引用

Physical Review A 2010年第6期81卷 060306(R)-060306(R)页

作者： Hauke Häseler Norbert Lütkenhaus Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo ON N2L 3G1 Canada and Quantum Information Theory Group Institut für Theoretische Physik I and Max Planck Institute for the Science of Light University of Erlangen-Nürnberg 91058 Erlangen Germany

We investigate several recently published benchmark criteria for storage or transmission of continuous-variable quantum information. A comparison reveals that criteria based on a Gaussian distribution of coherent states are most resilient to noise. We then address the issue of experimental resources and derive an equally strong benchmark, solely based on three coherent states and homodyne detection. This benchmark is further simplified in the presence of naturally occurring random phases, which remove the need for active input-state modulation.

关键词： Light transmission

来源：评论

学校读者我要写书评

暂无评论

Axiomatic Temporal Logic Programs Verification

Axiomatic Temporal Logic Programs Verification

引用

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

关键词： Semantics Writing Logic programming Computational modeling Laboratories Software

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：