Abstract
Heralded single-photon sources with on-demand readout are a key enabling technology for distributed photonic networks. Such sources have been demonstrated in both cryogenic solid-state and cold-atoms systems. Practical long-distance quantum communication may benefit from using technologically simple systems such as room-temperature atomic vapours. However, atomic motion has so far limited the single-excitation lifetime in such systems to the microsecond range. Here we demonstrate efficient heralding and readout of single collective excitations created in warm caesium vapour. Using the principle of motional averaging we achieve a collective excitation lifetime of 0.27 ± 0.04 ms, two orders of magnitude larger than previously achieved for single excitations in room-temperature sources. We experimentally verify non-classicality of the light-matter correlations by observing a violation of the Cauchy-Schwarz inequality with R = 1.4 ± 0.1 > 1. Through spectral and temporal analysis we investigate the readout noise that limits single-photon operation of the source.
Highlights
Heralded single-photon sources with on-demand readout are a key enabling technology for distributed photonic networks
quantum repeater (QR) can alleviate the losses in the optical fibres used to distribute quantum information over long distances, thereby increasing the distance over which entanglement can be efficiently distributed by means of entanglement swapping[5]
Many attempts to realize such schemes are based on the DuanLukin-Cirac-Zoller (DLCZ) protocol for atomic ensembles[6], where quantum information is stored in collective degrees of freedom of the ensembles
Summary
Heralded single-photon sources with on-demand readout are a key enabling technology for distributed photonic networks Such sources have been demonstrated in both cryogenic solid-state and cold-atoms systems. Coherent optical interaction with NV centres at room temperature remains a challenge[27] due to severely broadened optical transitions These memories can not directly be employed for quantum communication. Short-lived quantum memories have been demonstrated in warm vapours[28,29], but thermal atomic motion impedes long life spans of the generated collective excitations or stored light[30–32] since atoms rapidly leave the interaction region due to thermal motion. Anti-relaxation coating of the container walls has enabled continuous-variable quantum memory of a few milliseconds[38] and classical light storage up to 0.43 s39, but non-classical correlations for single excitations on such time scale remain to be observed. By extending the interaction time so that atoms traverse the interaction region multiple times, the average interaction of each atom with the light is the same, enabling coherent interaction with the symmetric collective atomic mode used for storage
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