scholarly journals Optimal Unambiguous Discrimination And Quantum Nonlocality Without Entanglement: Locking And Unlocking By Post-Measurement Information

2021 ◽  
Author(s):  
Donghoon Ha ◽  
Jeong San Kim
Keyword(s):  
Quantum Nonlocality ◽  
Measurement Information ◽  
Minimum Error ◽  
Separable States ◽  
Unambiguous Discrimination ◽  
State Discrimination

Abstract The phenomenon of nonlocality without entanglement(NLWE) arises in discriminating multi-party quantum separable states. Recently, it has been found that the post-measurement information about the prepared subensemble can lock or unlock NLWE in minimum-error discrimination of non-orthogonal separable states. Thus it is natrual to ask whether the availability of the post-measurement information can influence on the occurrence of NLWE even in other state-discrimination stratigies. Here, we show that the post-measurement information can be used to lock as well as unlock the occurence of NLWE in terms of optimal nambiguous discrimination. Our results can provide a useful application for hiding or sharing information based on non-orthogonal separable states.

scholarly journals Quantum nonlocality without entanglement depending on nonzero prior probabilities in optimal unambiguous discrimination

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Donghoon Ha ◽  
Jeong San Kim
Keyword(s):  
Quantum State ◽  
Quantum States ◽  
Quantum Nonlocality ◽  
Quantum State Discrimination ◽  
Classical Communication ◽  
Minimum Error ◽  
Prior Probabilities ◽  
Separable States ◽  
Unambiguous Discrimination ◽  
State Discrimination

AbstractNonlocality without entanglement(NLWE) is a nonlocal phenomenon that occurs in quantum state discrimination of multipartite separable states. In the discrimination of orthogonal separable states, the term NLWE is used when the quantum states cannot be discriminated perfectly by local operations and classical communication. In this case, the occurrence of NLWE is independent of nonzero prior probabilities of quantum states being prepared. Recently, it has been found that the occurrence of NLWE can depend on nonzero prior probabilities in minimum-error discrimination of nonorthogonal separable states. Here, we show that even in optimal unambiguous discrimination, the occurrence of NLWE can depend on nonzero prior probabilities. We further show that NLWE can occur regardless of nonzero prior probabilities, even if only one state can be locally discriminated without error. Our results provide new insights into classifying sets of multipartite quantum states in terms of quantum state discrimination.

Multicopy programmable discriminators between two unknown qudit states with group-theoretic approach

2012 ◽  
Vol 12 (11&12) ◽  
pp. 1017-1033
Author(s):  
Tao Zhou ◽  
Jing Xin Cui ◽  
Xiaohua Wu ◽  
Gui Lu Long
Keyword(s):  
Theoretic Approach ◽  
Data Systems ◽  
Mixed States ◽  
Minimum Error ◽  
Unambiguous Discrimination ◽  
State Discrimination ◽  
Jordan Basis ◽  
Orthogonal Measurement ◽  
The Mean ◽  
Programmable Discriminator

The discrimination between two unknown states can be performed by a universal programmable discriminator, where the copies of the two possible states are stored in two program systems respectively and the copies of data, which we want to confirm, are provided in the data system. In the present paper, we propose a group-theretic approach to the multi-copy programmable state discrimination problem. By equivalence of unknown pure states to known mixed states and with the representation theory of $U(n)$ group, we construct the Jordan basis to derive the analytical results for both the optimal unambiguous discrimination and minimum-error discrimination. The POVM operators for unambiguous discrimination and orthogonal measurement operators for minimum-error discrimination are obtained. We find that the optimal failure probability and minimum-error probability for the discrimination between the mean input mixd states are dependent on the dimension of the unknown qudit states. We applied the approach to generalize the results of He and Bergou (2007) from qubit to qudit case, and we further solve the problem of programmable dicriminators with arbitrary copies of unknown states in both program and data systems.

Minimum guesswork discrimination between quantum states

2015 ◽  
Vol 15 (9&10) ◽  
pp. 737-758
Author(s):  
Weien Chen ◽  
Yongzhi Cao ◽  
Hanpin Wang ◽  
Yuan Feng
Keyword(s):  
Error Probability ◽  
Sufficient Conditions ◽  
Optimization Criterion ◽  
Quantum States ◽  
Actual State ◽  
Information Theoretic ◽  
Minimum Error ◽  
State Discrimination ◽  
Semidefinite Programming Problem ◽  
Necessary And Sufficient

Error probability is a popular and well-studied optimization criterion in discriminating non-orthogonal quantum states. It captures the threat from an adversary who can only query the actual state once. However, when the adversary is able to use a brute-force strategy to query the state, discrimination measurement with minimum error probability does not necessarily minimize the number of queries to get the actual state. In light of this, we take Massey's guesswork as the underlying optimization criterion and study the problem of minimum guesswork discrimination. We show that this problem can be reduced to a semidefinite programming problem. Necessary and sufficient conditions when a measurement achieves minimum guesswork are presented. We also reveal the relation between minimum guesswork and minimum error probability. We show that the two criteria generally disagree with each other, except for the special case with two states. Both upper and lower information-theoretic bounds on minimum guesswork are given. For geometrically uniform quantum states, we provide sufficient conditions when a measurement achieves minimum guesswork. Moreover, we give the necessary and sufficient condition under which making no measurement at all would be the optimal strategy.

scholarly journals Almost minimum error discrimination of N-ary weak coherent states by Jaynes-Cummings Hamiltonian dynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Min Namkung ◽  
Younghun Kwon
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum State ◽  
Coherent States ◽  
Quantum Information Processing ◽  
Hamiltonian Dynamics ◽  
Quantum State Discrimination ◽  
Minimum Error ◽  
State Discrimination

AbstractQuantum state discrimination of coherent states has been one of important problems in quantum information processing. Recently, R. Han et al. showed that minimum error discrimination of two coherent states can be nearly done by using Jaynes-Cummings Hamiltonian. In this paper, based on the result of R. Han et al., we propose the methods where minimum error discrimination of more than two weak coherent states can be nearly performed. Specially, we construct models which can do almost minimum error discrimination of three and four coherent states. Our result can be applied to quantum information processing of various coherent states.

scholarly journals State Discrimination With Post-Measurement Information

2008 ◽  
Vol 54 (9) ◽  
pp. 4183-4198 ◽  
Author(s):  
Manuel A. Ballester ◽  
Stephanie Wehner ◽  
Andreas Winter
Keyword(s):  
Measurement Information ◽  
State Discrimination
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