Avoiding entanglement sudden-death via measurement feedback control in a quantum network

TL;DR

This paper demonstrates that measurement feedback control can prevent entanglement sudden-death in a quantum network of two cavities, enhancing and stabilizing entanglement despite realistic signal loss.

Contribution

It introduces a feedback control method that avoids entanglement sudden-death and improves entanglement robustness in a quantum network.

Findings

Feedback control prevents entanglement sudden-death.

Entanglement is enhanced and stabilized by feedback.

Method is robust against detector signal loss.

Abstract

In this paper, we consider a linear quantum network composed of two distantly separated cavities that are connected via a one-way optical field. When one of the cavity is damped and the other is undamped, the overall cavity state obtains a large amount of entanglement in its quadratures. This entanglement however immediately decays and vanishes in a finite time. That is, entanglement sudden-death occurs. We show that the direct measurement feedback method proposed by Wiseman can avoid this entanglement sudden-death, and further, enhance the entanglement. It is also shown that the entangled state under feedback control is robust against signal loss in a realistic detector, indicating the reliability of the proposed direct feedback method in practical situations.