Plug-and-play unidimensional continuous-variable quantum key distribution

Numerous continuous-variable quantum key distribution (CV-QKD) schemes are based on the Gaussian modulation, which is carried out in conjugate quadratures. In order to simplify the traditional protocols, as well as improving the security of the system, we propose the plug-and-play unidimensional CV-QKD protocol, which waives the necessity of propagating a local oscillator (LO) between legitimate users and generates a real local LO for quantum measurement. The new protocol utilizes only one phase modulator rather than two, which is different from the dual-phase-modulated coherent-states protocol that we proposed earlier. The prepare-and-measure and entanglement-based schemes are described. The security of the new protocol against collective attacks in a Gaussian channel is analyzed, and the security boundary is derived, which is achieved by establishing the relationship between the uncertain parameters of the unmodulated quadrature. The performance of it is analyzed in both asymptotic and finite-size cases. Such an efficient scheme not only provides a way of removing the security loopholes associated with the transmitting LO, but also eliminates the need for one of the phase modulators, and thus will facilitate commercialization of continuous-variable quantum key distribution.