Plug-and-Play Continuous Variable Measurement-Device-Independent Quantum Key Distribution

In this paper, a continuous variable (CV) measurement-device-independent (MDI) quantum key distribution (QKD) protocol using Gaussian modulated coherent states is proposed. The MDI is first proposed to resist the attacks on the detection equipment by introducing an untrusted relay. However, the necessity of propagation of local oscillator between legitimate users and the relay makes the implementation of CV-MDI-QKD highly impractical. By introducing the plug-and-play (P&P) technique into CV-MDI-QKD, the problems of polarization drifts caused by environmental disturbance and the security loopholes during the local oscillator transmission are solved naturally. The proposed scheme is superior to the previous CV-MDI-QKD protocol on the aspect of implementation. The security bounds of the P&P CV-MDI-QKD under the Gaussian collective attack are analyzed. It is believed that the technique presented in this paper can be extended to quantum network.