Local optimality of a coherent feedback scheme for distributed entanglement generation: the idealized infinite bandwidth limit

TL;DR

This paper proves a local optimality property of a specific coherent feedback scheme for distributed EPR entanglement generation in the idealized infinite bandwidth limit, highlighting its effectiveness and optimality within a class of similar configurations.

Contribution

It establishes the local optimality of a coherent feedback configuration for entanglement generation in the idealized infinite bandwidth limit, providing explicit verification criteria.

Findings

The feedback scheme is locally optimal within a class of similar configurations.

Infinite bandwidth limit simplifies analysis and accurately approximates low-frequency entanglement.

The scheme effectively generates EPR entanglement in the idealized limit.

Abstract

The purpose of this paper is to prove a local optimality property of a recently proposed coherent feedback configuration for distributed generation of EPR entanglement using two nondegenerate optical parametric amplifiers (NOPAs) in the idealized infinite bandwidth limit. This local optimality is with respect to a class of similar coherent feedback configurations but employing different unitary scattering matrices, representing different scattering of propagating signals within the network. The infinite bandwidth limit is considered as it significantly simplifies the analysis, allowing local optimality criteria to be explicitly verified. Nonetheless, this limit is relevant for the finite bandwidth scenario as it provides an accurate approximation to the EPR entanglement in the low frequency region where EPR entanglement exists.