Distributional Transform Based Information Reconciliation

In this paper we present an information reconciliation protocol designed for Continuous-Variable QKD using the Distributional Transform. By combining tools from copula and information theories, we present a method for extracting independent symmetric Bernoulli bits for Gaussian modulated CVQKD protocols, which we called the Distributional Transform Expansion (DTE). We derived the expressions for the maximum reconciliation efficiency for both homodyne and heterodyne measurement, which, for the last one, efficiency greater than 0.9 is achievable at signal to noise ratio lower than -3.6 dBComment: 6 pages, 3 Figures, Conference pape

A method for Sampling Bernoulli Variables

We introduce new method for generating correlated or uncorrelated Bernoulli random variables by using the binary expansion of a continuous random variable with support on the unit interval. We show that when this variable has a symmetric probability density function around 12 , its binary expansion provides equiprobable bits over {0, 1}. In addition we prove that when the random variable is uniformly distributed over [0, 1], its binary expansion generates independent Bernoulli random variables. Moreover, we give examples where, by choosing some parameterized nonuniform probability density functions over [0, 1], samples of Bernoulli variables with specific correlation values are generated.Comment: 11 pages, 3 figure

Converging State Distributions for Discrete Modulated CVQKD Protocols

Consider the problem of using a finite set of coherent states to distribute secret keys over a quantum channel. It is known that computing the exact secret key rate in this scenario is intractable due to the infinite dimensionality of the Hilbert spaces and usually one computes a lower bound using a Gaussian equivalent bipartite state in the entangled based version of the protocol, which leads to underestimating the actual protocol capability of generating secret keys for the sake of security. Here, we define the QKD protocol's non-Gaussianity, a function quantifying the amount of secret key rate lost due to assuming a Gaussian model when a non-Gaussian modulation was used, and develop relevant properties for it. We show that if the set of coherent states is induced by a random variable approaching the AWGN channel capacity, then the protocol's non-Gaussianity vanishes, meaning that there is no loss of secret key rate due to the use of a Gaussian model for computing bound on the secret key rate. The numerical results show that by using a 256-QAM with Gauss-Hermite shaping, the loss of secret key rate quickly falls below $10^{-5}$ as the distance increases.Comment: 14 pages, 6 figure

Quantum-Mechanical Information Content of Multiples Hartree-Fock Solutions. The Multi-Reference Hartree-Fock Configuration Interaction Method

International audience(CE 13 juillet 2016, n° 387763, Lebon ; AJDA 2016. 1479 ; ibid. 1629, chron. L. Dutheillet de Lamothe et G. Odinet ; AJFP 2016. 356, et les obs. ; AJCT 2016. 572, obs. M.-C. Rouault ; RFDA 2016. 927, concl. O. Henrard