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

摘要

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