Composable security of unidimensional continuous-variable quantum key distribution

TL;DR

This paper analyzes the composable security of a simplified unidimensional continuous-variable quantum key distribution protocol, demonstrating its security against collective attacks and comparing its performance to symmetric protocols through numerical simulations.

Contribution

It establishes the composable security of the UCVQKD protocol with finite-size effects considered, providing the tightest security bounds and performance comparison with symmetric protocols.

Findings

Secure against collective attacks

Tightest security bounds established

Comparable asymptotic secret key rate to symmetric protocols

Abstract

We investigate the composable security of unidimensional contin- uous variable quantum key distribution (UCVQKD), which is based on the Gaussian modulation of a single quadrature of the coherent-state of light, aiming to provide a simple implementation of key distribution compared to the symmetrically modulated Gaussian coherent-state protocols. This protocol neglects the necessity in one of the quadrature modulation in coherent-states and hence reduces the system complexity. To clarify the influence of finite-size effect and the cost of performance degeneration, we establish the relation- ship of the balanced parameters of the unmodulated quadrature and estimate the precise secure region. Subsequently, we illustrate the composable security of the UCVQKD protocol against collective attacks and achieve the tightest bound of the UCVQKD protocol. Numerical simulations show the asymptotic secret key rate of the UCVQKD protocol, together with the symmetrically modulated Gaussian coherent-state protocols.