Excess noise in bandwidth-resource-efficient entanglement distribution

In this work, we emphasize the importance of properly designing a bandwidth-resource-efficient entanglement distribution system. In particular, we point out that inappropriate setting of wavelength demultiplexing channel bandwidth with respect to pump spectral width could affect entanglement quality. It is widely known that the photon coherence length can be made longer than pump pulsewidth by narrowband filtering so as to improve photon temporal coherence, however, the excess noise that accompanies narrowband filtering has not been studied. The use of narrowband sources of entangled photon-pairs avoids this problem but one needs to wavelength-multiplex many such narrowband sources in order to implement bandwidth-resource-efficient entanglement distribution. We show how to reduce excess noise while maintaining a high photon temporal coherence for a bandwidth-resource-efficient system that uses broadband sources.