Quantum key distribution device with coherent states

Abstract

We report on both theoretical and experimental aspects of a fully implemented quantum key distribution device with coherent states. This system features a final key rate of more than 2 kb/s over 25 km of optical fiber. It comprises all required elements for field operation: a compact optical setup, a fast secret bit extraction using efficient LDPC codes, privacy amplification algorithms and a classical channel software. Both hardware and software are operated in real time.

Improving the maximum transmission distance of continuous-variable quantum key distribution using a noiseless amplifier

“…Alice and Bob finally extract a secret key from the correlated data by performing classical data processing and authenticated classical communication. This protocol offers a simple experimental implementation [3,[30][31][32] and is secure against finite-size collective attacks [33] as well as arbitrary attacks in the asymptotic limit of arbitrary long keys [7].…”

“…This matrix contains all the information needed to establish the secret key rate for collective attacks [30],…”

Asymptotic security of binary modulated continuous-variable quantum key distribution under collective attacks

“…The experimental feasibility of various CV-QKD schemes using coherent states as input and variations of homodyne detection has already been demonstrated [7,8,13,14,15,16,17]. Although promising from a technological point of view as the measurement can operate at high repetition rates, the efficiency of these schemes seems to be limited by the classical post-processing protocol.…”

Security of Continuous-Variable Quantum Key Distribution Against General Attacks

“…Γ 4 ) and from the eigenvalue ν 3 of the matrix Γ hom 2 (resp. Γ hom 4 or Γ het 4 depending on the nature of the measurement ) corresponding to the covariance matrix of Alice's state given the result y of Bob's homodyne (or heterodyne) measurement [8].…”

“…Such a channel models accurately the effect of typical optical fibers on the quadratures of the EM field. Using theorems about the optimality of Gaussian attacks, such schemes were proven secure against collective attacks [4,5,6] then later against general attacks [7] and were also successfully implemented [8,9].…”