  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.
