End-to-end entanglement in a coherent feedback interconnection of three nondegenerate optical parametric amplifiers

In previous work we have shown that a dual nondegenerate optical parametric amplifier (NOPA) coherent feedback network tolerates transmission losses better and has stronger entanglement (i.e., enhanced two-mode squeezing) than a single NOPA over the same transmission distance. The aim of this paper is to investigate stability, entanglement degree and power consumption of a coherent feedback interconnection of three NOPAs, which connects two spatially separated parties over two transmission channels. The influence of transmission losses in the transmission channels is considered and numerical calculations are given to illustrate advantages for entanglement generation of the triple-NOPA coherent feedback network over a dual-NOPA coherent feedback system.