  Future quantum repeater architectures, capable of efficiently distributing
information encoded in quantum states of light over large distances, will
benefit from multiplexed photonic quantum memories. In this work we demonstrate
a temporally multiplexed quantum repeater node in a laser-cooled cloud of
$^{87}$Rb atoms. We employ the DLCZ protocol where pairs of photons and single
collective spin excitations (so called spin waves) are created in several
temporal modes using a train of write pulses. To make the spin waves created in
different temporal modes distinguishable and enable selective readout, we
control the dephasing and rephasing of the spin waves by a magnetic field
gradient, which induces a controlled reversible inhomogeneous broadening of the
involved atomic hyperfine levels. We demonstrate that by embedding the atomic
ensemble inside a low finesse optical cavity, the additional noise generated in
multi-mode operation is strongly suppressed. By employing feed forward readout,
we demonstrate distinguishable retrieval of up to 10 temporal modes. For each
mode, we prove non-classical correlations between the first and second photon.
Furthermore, an enhancement in rates of correlated photon pairs is observed as
we increase the number of temporal modes stored in the memory. The reported
capability is a key element of a quantum repeater architecture based on
multiplexed quantum memories.
