Fig. 1

Proposal for single-photon spatial routing and multiplexing for multi-photon state generation. A single-photon resolving camera registers consecutive frames during the quantum memory write-in process. Each detection heralds creation of a spin-wave excitation in the atomic ensemble quantum memory with a wavevector determined by the position (k _xi , k _yi ) at which i-th photon was registered. Acquisition and write-in continue until the desired number of excitations has been created. At this time a photonic switch is reconfigured to channel photons from conjugate directions stored in a classical memory and subsequently the readout pulse is applied to convert stored spin-wave excitations to the requested number of photons, which will be used later, e.g., in the quantum circuit