scholarly journals Unambiguous state discrimination of coherent states with linear optics: Application to quantum cryptography

2002 ◽  
Vol 66 (4) ◽  
Author(s):  
S. J. van Enk
Keyword(s):  
Quantum Cryptography ◽  
Coherent States ◽  
Linear Optics ◽  
State Discrimination ◽  
Unambiguous State Discrimination

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 Zero-error attacks and detection statistics in the coherent one-way protocol for quantum cryptography

2007 ◽  
Vol 7 (7) ◽  
pp. 639-664 ◽  
Author(s):  
C. Branciard ◽  
N. Gisin ◽  
N. Lutkenhaus ◽  
V. Scarani
Keyword(s):  
Quantum Cryptography ◽  
Careful Analysis ◽  
Beam Splitting ◽  
Statistical Parameters ◽  
Experimental Scheme ◽  
State Discrimination ◽  
Unambiguous State Discrimination ◽  
Better Than

This is a study of the security of the Coherent One-Way (COW) protocol for quantum cryptography, proposed recently as a simple and fast experimental scheme. In the zero-error regime, the eavesdropper Eve can only take advantage of the losses in the transmission. We consider new attacks, based on unambiguous state discrimination, which perform better than the basic beam-splitting attack, but which can be detected by a careful analysis of the detection statistics. These results stress the importance of testing several statistical parameters in order to achieve higher rates of secret bits.

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.

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.

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