Improving entanglement concentration of Gaussian states by local displacements

TL;DR

This paper explores enhancing entanglement concentration of Gaussian states using local displacements instead of squeezing, demonstrating improved entanglement through local operations in continuous-variable quantum systems.

Contribution

It introduces a novel method of using local coherent displacements to improve entanglement concentration, replacing the need for local squeezing in Gaussian states.

Findings

Local displacements can enhance entanglement similarly to squeezing.

Displacement-based protocols are simpler to implement experimentally.

The mechanism of entanglement increase is clarified through analysis.

Abstract

We investigate entanglement concentration of continuous-variable Gaussian states by local single-photon subtractions combined with local Gaussian operations. We first analyze the local squeezing-enhanced entanglement concentration protocol proposed very recently by Zhang and van Loock [e-print: arXiv:1103.4500 (2011)] and discuss the mechanism by which local squeezing before photon subtraction helps to increase the entanglement of the output state of the protocol. We next show that a similar entanglement improvement can be achieved by using local coherent displacements instead of single-mode squeezing.