Abstract
Parallelized quantum information processing requires tailored quantum memories to simultaneously handle multiple photons. The spatial degree of freedom is a promising candidate to facilitate such photonic multiplexing. Using a single-photon resolving camera, we demonstrate a wavevector multiplexed quantum memory based on a cold atomic ensemble. Observation of nonclassical correlations between Raman scattered photons is confirmed by an average value of the second-order correlation function g_{{mathrm{S,AS}}}^{{mathrm{(2)}}} = 72 pm 5 in 665 separated modes simultaneously. The proposed protocol utilizing the multimode memory along with the camera will facilitate generation of multi-photon states, which are a necessity in quantum-enhanced sensing technologies and as an input to photonic quantum circuits.
Highlights
Parallelized quantum information processing requires tailored quantum memories to simultaneously handle multiple photons
The experimental realization is accomplished through multiplexing of angular emission modes of a single quantum memory[27] and by employing a spatially resolved single-photon detection
We have demonstrated a quantum memory-enabled source of spatially structured nonclassical light based on a principle of wavevector multiplexing
Summary
Parallelized quantum information processing requires tailored quantum memories to simultaneously handle multiple photons. Memoryless systems, hundreds of modes have been obtained within the spatial domain of spontaneous parametric downconversion[31,32,33] or by means of frequency-time entanglement[18,34,35,36,37,38] Most applications such as the DLCZ protocol[21], enhanced photon generation[26,27,39], or even linear optical quantum computing[30] require or greatly benefit from a multimode quantum memory. These schemes suffer from the limitation given by difficulty in trapping large ensembles as well as hinder heralded simultaneous excitation of all modes In consequence, they are rendered useful only for the DLCZ quantum repeater[21], but neither for quantum imaging[42,43,44] nor enhancing rate of the photonic state generation[18,19,26,27]. We achieve the quantum memory lifetime of >50 μs, which combined with the multimode capacity invites real-time feedback processing of stored excitations[45] and paves the way toward promptly achieving fast generation of single- and multi-photon states[26,27]
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