The collective squeezing operation for pure Gaussian states with unknown parameters

Abstract

A continuous-variable analog of the Deutsch's distillation protocol locally operating with two copies of the same Gaussian state is suggested. Irrespectively of the impossibility of Gaussian state distillation, we reveal that this protocol is able to perform a squeezing concentration of the Gaussian states with unknown displacement. Since this operation cannot be implemented using only single copy of the state, it is a new application of the distillation protocol which utilizes two copies of the same Gaussian state.