Shared-reference-frame-independent continuous-variable quantum key distribution.

Abstract

The protocol of continuous-variable quantum key distribution based on quadrature modulation of coherent states and heterodyne quadrature detection, which does not rely on sharing either a local oscillator or pilot tones, is proposed. Using unidimensional single-quadrature encoding, we suggest alignment of the measurement bases relying on the asymmetry of the phase-space distribution of the modulated states. By rotating the bases so that the maximum quadrature variance is observed, the remote communicating party can identify the signal quadrature direction. Depending on the coherence time of the signal and the repetition rate of the system, the necessary statistics can be accumulated to minimize misalignment between the preparation and measurement bases. We address the issue of residual bases misalignment in the suggested shared-reference-frame-independent continuous-variable quantum key distribution protocol and show that it is feasible with state-of-the-art techniques. The result paves the way for low-cost and simplified quantum communication schemes, which are independent of any shared phase reference and are therefore immune to potential quantum hacking attacks on the local oscillator or pilot tones.