OPTIMAL UNAMBIGUOUS DISCRIMINATION OF TWO FINITE-DIMENSIONAL COHERENT STATES

2009 ◽  
Vol 07 (02) ◽  
pp. 517-528 ◽  
Author(s):  
M. REZAEI ◽  
M. R. REZAPOUR ◽  
M. A. FASIHI
Keyword(s):  
Success Rate ◽  
Coherent States ◽  
Decomposition Method ◽  
Prior Probability ◽  
Exact Analytical Solution ◽  
Prior Probabilities ◽  
Unambiguous Discrimination ◽  
State Discrimination ◽  
Finite Dimensional ◽  
Unambiguous State Discrimination

An exact analytical solution to the optimal unambiguous state discrimination involving two finite-dimensional coherent states that occur with given prior probabilities is presented using the Lewenstein–Sanpera decomposition method. Furthermore, a numerical method is advised for efficient solving of the unambiguous state discrimination of the two finite-dimensional coherent states with the same dimensions. In this manner, it is shown that the maximum success rate for the unambiguous states discrimination of the two finite-dimensional coherent states with the arbitrary prior probability is decreased by increasing the dimensionality of the finite-dimensional coherent states. Also, the success rate for the unambiguous states discrimination of the two coherent states satisfies the upper bound proportional to the fidelity of the states for a given prior probability.

scholarly journals Heralded orthogonalisation of coherent states and their conversion to discrete-variable superpositions

2017 ◽  
Vol 4 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Regina Kruse ◽  
Christine Silberhorn ◽  
Tim Bartley
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Coherent States ◽  
Quantum Information Processing ◽  
Fundamental Property ◽  
Discrete Variable ◽  
Successful Operation ◽  
State Discrimination ◽  
Unambiguous State Discrimination

Abstract The nonorthogonality of coherent states is a fundamental property which prevents them from being perfectly and deterministically discriminated. Here, we present an experimentally feasible protocol for the probabilistic orthogonalisation of a pair of coherent states, independent of their amplitude and phase. In contrast to unambiguous state discrimination, a successful operation of our protocol is heralded without measuring the states. As such, they remain suitable for further manipulation and the obtained orthogonal states serve as a discretevariable basis. Therefore, our protocol doubles as a simple continuous-to-discrete variable converter, which may find application in hybrid continuous-discrete quantum information processing protocols.

scholarly journals Quantum Contextual Advantage Depending on Nonzero Prior Probabilities in State Discrimination of Mixed Qubit States

Entropy ◽  
2021 ◽  
Vol 23 (12) ◽  
pp. 1583
Author(s):  
Jaehee Shin ◽  
Donghoon Ha ◽  
Younghun Kwon
Keyword(s):  
Prior Probability ◽  
The State ◽  
Mixed States ◽  
Minimum Error ◽  
Prior Probabilities ◽  
Quantum Properties ◽  
State Discrimination ◽  
The Given ◽  
Qubit States ◽  
Selection Of

Recently, Schmid and Spekkens studied the quantum contextuality in terms of state discrimination. By dealing with the minimum error discrimination of two quantum states with identical prior probabilities, they reported that quantum contextual advantage exists. Meanwhile, if one notes a striking observation that the selection of prior probability can affect the quantum properties of the system, it is necessary to verify whether the quantum contextual advantage depends on the prior probabilities of the given states. In this paper, we consider the minimum error discrimination of two states with arbitrary prior probabilities, in which both states are pure or mixed. We show that the quantum contextual advantage in state discrimination may depend on the prior probabilities of the given states. In particular, even though the quantum contextual advantage always exists in the state discrimination of two nonorthogonal pure states with nonzero prior probabilities, the quantum contextual advantage depends on prior probabilities in the state discrimination of two mixed states.

scholarly journals Безошибочное различение когерентных состояний двухмодового оптического поля

2020 ◽  
Vol 128 (8) ◽  
pp. 1171
Author(s):  
М.М. Эскандери ◽  
Д.Б. Хорошко ◽  
С.Я. Килин
Keyword(s):  
Optical Communication ◽  
Optical Communications ◽  
Communication Channel ◽  
Optical Field ◽  
Complex Conjugation ◽  
Unambiguous Discrimination ◽  
State Discrimination ◽  
High Level ◽  
Optical Communication Channel ◽  
Unambiguous State Discrimination

The procedure of a quantum measurement, the unambiguous state discrimination, is studied for the case of four two-mode coherent states of the optical field, interesting for information transmission via an optical communication channel. It is shown that a complex conjugation of the amplitude of one of the modes results in a better distinguishability of the states. An interferometric scheme is suggested for unambiguous discrimination of such states and the probability of successful discrimination is found. Applications of the considered state set are discussed for quantum cryptography, quantum teleportation and optical communications with a high level of loss.

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.

scholarly journals Sequential attacks against differential-phase-shift quantum key distribution with weak coherent states

2007 ◽  
Vol 7 (7) ◽  
pp. 665-688
Author(s):  
M. Curty ◽  
L.L. Zhang ◽  
H.-K. Lo ◽  
N. Lutkenhaus
Keyword(s):  
Phase Shift ◽  
Quantum Key Distribution ◽  
Coherent States ◽  
Key Distribution ◽  
Upper Bounds ◽  
Coherent Light ◽  
Differential Phase Shift ◽  
Differential Phase ◽  
State Discrimination ◽  
Unambiguous State Discrimination

We investigate limitations imposed by sequential attacks on the performance of differential-phase-shift quantum key distribution protocols that use pulsed coherent light. In particular, we analyze two sequential attacks based on unambiguous state discrimination and minimum error discrimination, respectively, of the signal states emitted by the source. Sequential attacks represent a special type of intercept-resend attacks and, therefore, they provide ultimate upper bounds on the maximal distance achievable by quantum key distribution schemes.

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