  Quantum memories are key components in quantum information networks. Their
ability to store and retrieve information on demand makes repeat-until-success
strategies scalable. Warm alkali-metal vapours are interesting candidates for
the implementation of such memories, thanks to their long storage times and
experimental simplicity. Operation with the Raman protocol enables high
time-bandwidth products, which allows for multiple synchronisation trials of
probabilistically operating quantum gates via memory-based temporal
multiplexing. This makes the Raman memory a promising tool, whose broad
spectral bandwidth facilitates direct interfacing with other photonic
primitives, such as single photon sources. Here, such a light-matter interface
is implemented in a warm caesium vapour. Firstly, we study the storage of
polarisation-encoded information in the memory. High quality polarisation
preservation for bright coherent state input signals can be achieved, when
operating the Raman memory in a dual-rail configuration inside a polarisation
interferometer. Secondly, heralded single photons are stored in the memory. To
this end, the memory is operated on-demand by feed-forward of source heralding
events, which is a key technological capability. Prior to storage, single
photons are produced in a spontaneous parametric down conversion source, whose
bespoke design spectrally tailors the photons to the memory acceptance line.
The faithful retrieval of stored single photons is found to be currently
limited by noise in the memory, with a signal-to-noise ratio of 0.3 in the
memory output. Nevertheless, a clear influence of the input's quantum nature is
observed in the retrieved light by measuring signal's photon statistics.
Finally, the memory noise processes are examined in detail. Four-wave-mixing
noise is determined as the sole important noise source for the Raman memory.
