Cross talk compensation in multimode continuous-variable entanglement distribution

Abstract

Two-mode squeezed states are scalable and robust entanglement resources for continuous-variable and hybrid quantum information protocols that are realized at a distance. We consider the effect of a linear cross talk in the multimode distribution of two-mode squeezed states propagating through parallel similar channels. First, to reduce degradation of the distributed Gaussian entanglement, we show that the initial two-mode squeezing entering the channel should be optimized already in the presence of a small cross talk. Second, we suggest simultaneous optimization of relative phase between the modes and their linear coupling on a receiver side prior to the use of entanglement, which can fully compensate the cross talk once the channel transmittance is the same for all the modes. For the realistic channels with similar transmittance values for either of the modes, the cross talk can be still largely compensated. This method relying on the mode interference overcomes an alternative method of entanglement localization in one pair of modes using measurement on another pair and feed-forward control. Our theoretical results pave the way to more efficient use of multimode continuous-variable photonic entanglement in scalable quantum networks with cross talk.

Redundancy and Synergy of an Entangling Cloner in Continuous-Variable Quantum Communication

“…The effect vanishes, when the conditioning is taken on both the modes of an auxiliary cloner. Note, that we consider interaction between two modes, one of each cloner, while if both modes of each cloner are interacting, this can be seen as a correlated cross talk and can be effectively removed for entanglement distribution [ 18 ] and QKD [ 19 ].…”