  Photonics offers a route to fast and distributed quantum computing in ambient
conditions, provided that photon sources and logic gates can be operated
deterministically. Quantum memories, capable of storing and re-emitting photons
on demand, enable quasi-deterministic operations by synchronising stochastic
events. We recently interfaced a Raman-type quantum memory with a
travelling-wave heralded photon source. Here we discuss the trade-space for the
spectral characteristics of such sources, and we present measurements of our
source, which represents a practical compromise enabling passive stability,
high brightness in a single-pass configuration, high purity and good matching
to our Cs vapour memory.
