Quantifying non-Markovianity of continuous-variable Gaussian dynamical maps

Non-Markovianity of Gaussian Channels.

We introduce a necessary and sufficient criterion for the non-Markovianity of Gaussian quantum dynamical maps based on the violation of divisibility. The criterion is derived by defining a general vectorial representation of the covariance matrix which is then exploited to determine the condition for the complete positivity of partial maps associated with arbitrary time intervals. Such construc...

Continuous iteration of dynamical maps

Continuous-variable quantum cryptography is secure against non-Gaussian attacks.

A general study of arbitrary finite-size coherent attacks against continuous-variable quantum cryptographic schemes is presented. It is shown that, if the size of the blocks that can be coherently attacked by an eavesdropper is fixed and much smaller than the key size, then the optimal attack for a given signal-to-noise ratio in the transmission line is an individual Gaussian attack. Consequent...

Quantum Key Distribution using Continuous-variable non-Gaussian States

In this work we present a quantum key distribution protocol using continuous-variable nonGaussian states, homodyne detection and post-selection. The employed signal states are the Photon Added then Subtracted Coherent States (PASCS) in which one photon is added and subsequently one photon is subtracted. We analyze the performance of our protocol, compared to a coherent state based protocol, for...

Continuous-variable Gaussian analog of cluster states

We present a continuous-variable CV Gaussian analog of cluster states, a new class of CV multipartite entangled states that can be generated from squeezing and quantum nondemolition coupling HI= XAXB. The entanglement properties of these states are studied in terms of classical communication and local operations. The graph states as general forms of the cluster states are presented. A chain for...