  Quantum repeater networks require independent quantum memories capable of
storing and retrieving indistinguishable photons to perform high-repetition
entanglement swapping operations. The ability to perform these coherent
operations at room temperature is of prime importance to the realization of
scalable quantum networks. We perform Hong-Ou-Mandel (HOM) interference between
photonic polarization qubits stored and retrieved from two sets of independent
room-temperature quantum memories. We show a steady improvement in memory
parameters and visibilities, culminating in a high quantum memory HOM
visibility of 43%, compared to the 48% no-memory limit of our set-up. These
results lay the groundwork for future applications using large-scale
memory-assisted quantum networks.
