Disentanglement in Bipartite Continuous-Variable Systems

TL;DR

This paper examines how entanglement in bipartite continuous-variable systems is affected by partial losses, identifying conditions for its survival and providing criteria for Gaussian states.

Contribution

It introduces criteria for the robustness of entanglement under partial losses and offers a framework for analyzing continuous-variable entanglement in complex systems.

Findings

Entanglement can vanish completely due to partial losses.

States with extreme squeezing may become separable after propagation.

Derived criteria determine when entanglement survives in lossy channels.

Abstract

Entanglement in bipartite continuous-variable systems is investigated in the presence of partial losses, such as those introduced by a realistic quantum communication channel, e.g. by propagation in an optical fiber. We find that entanglement can vanish completely for partial losses, in a situa- tion reminiscent of so-called entanglement sudden death. Even states with extreme squeezing may become separable after propagation in lossy channels. Having in mind the potential applications of such entangled light beams to optical communications, we investigate the conditions under which entanglement can survive for all partial losses. Different loss scenarios are examined and we derive criteria to test the robustness of entangled states. These criteria are necessary and sufficient for Gaussian states. Our study provides a framework to investigate the robustness of continuous-variable entanglement in more complex multipartite systems.