  Maximizing the information transmission rate through quantum channels is
essential for practical implementation of quantum communication. Time-division
multiplexing is an approach for which the ultimate rate requires the ability to
manipulate and detect single photons on ultrafast timescales while preserving
their quantum correlations. Here we demonstrate the demultiplexing of a train
of pulsed single photons using time-to-frequency conversion while preserving
their polarization entanglement with a partner photon. Our technique converts a
pulse train with 2.69 ps spacing to a frequency comb with 307 GHz spacing which
may be resolved using diffraction techniques. Our work enables ultrafast
multiplexing of quantum information with commercially available single-photon
detectors.
