Unambiguous state discrimination in quantum cryptography with weak coherent states

Abstract

The use of linearly independent signal states in realistic implementations of quantum key distribution (qkd) enables an eavesdropper to perform unambiguous state discrimination. We explore quantitatively the limits for secure qkd imposed by this fact taking into account that the receiver can monitor to some extend the photon number statistics of the signals even with todays standard detection schemes. We compare our attack to the beamsplitting attack and show that security against beamsplitting attack does not necessarily imply security against the attack considered here.03.67. Dd, 03.65.Bz, 42.79.Sz

Optimal discrimination of mixed quantum states involving inconclusive results

“…Besides being a theoretically interesting problem, the quantum-state discrimination has also found practical applications in quantum information processing. In particular, the optimal unambiguous quantum-state discrimination represents a simple and experimentally feasible attack on the quantum key distribution protocols [26,27]. Recently, some optimal discrimination POVMs have been realized experimentally and the Helstrom as well as the IDP bounds have been attained [28,29,30,31].…”

Finding optimal strategies for minimum-error quantum-state discrimination

“…Many of the theoretically discovered optimal devices have already been realized experimentally, mainly with polarized light [18][19][20][21]. As an example of the practical importance of the optimal decision schemes let us mention their use for the eavesdropping on quantum cryptosystems [22,23].The purpose of this paper is to develop universal method for optimizing ambiguous discrimination between generic quantum states.Assume that Alice sets up M different sources of quantum systems living in p-dimensional Hilbert space. The complete quantum-mechanical description of each source * e-mail: rehacek@phoenix.inf.upol.cz is provided by its density matrix.…”

“…Many of the theoretically discovered optimal devices have already been realized experimentally, mainly with polarized light [18][19][20][21]. As an example of the practical importance of the optimal decision schemes let us mention their use for the eavesdropping on quantum cryptosystems [22,23].…”

Unambiguous modification of nonorthogonal single- and two-photon polarization states

“…Today, USD plays an important role in quantum communication and quantum computing, being at the core of many quantum cryptographic schemes and probabilistic quantum algorithms [14]. It can be used, for instance, as a model for efficient attack in quantum cryptography [15,16].…”