Multipartite Continuous-Variable Entanglement Distribution with Separable Gaussian States

Entangling quantum systems at distant locations is a newly discovered counterintuitive phenomenon. However, the generation effect will be reduced by imperfections of practical devices. In this paper, we demonstrate a Gaussian process approach for the scheme design of multipartite continuous-variable (CV) entanglement generation and distribution by using separable Gaussian states, which are superimposed on the beam splitters with the single auxiliary state, rendering the desirable CV entangled states. The superimposing operation not only can avoid the complexity and imperfection of the practical state-superimposing operations, which defends the eavesdropper as the auxiliary mode which is separable, but also can be regulated flexibly by performing suitable displacements with the regulated parameter of the initial states before being sent to the beam splitters to optimize the performance.