  To advance the full potential of quantum networks one should be able to
distribute quantum resources over long distances at appreciable rates. As a
consequence, all components in the networks need to have large multimode
capacity to manipulate photonic quantum states. Towards this end, a multimode
photonic quantum memory, especially one operating at telecom wavelength,
remains a key challenge. Here we demonstrate a spectro-temporally multiplexed
quantum memory at 1532 nm. Multimode quantum storage of telecom-band heralded
single photons is realized by employing the atomic frequency comb protocol in a
10-m-long cryogenically cooled erbium doped silica fibre. The multiplexing
encompasses five spectral channels - each 10 GHz wide - and in each of these up
to 330 temporal modes, resulting in the simultaneous storage of 1650 modes of
single photons. Our demonstrations open doors for high-rate quantum networks,
which are essential for future quantum internet.
