New J. Phys. 16, 033042 (2014)
'Rephased' amplified spontaneous emission (RASE) from an atomic ensemble could in principle lead to on-demand production of single photons with a high efficiency and fidelity, according to an international team of researchers. Robin Stevenson and co-workers from Australia, the UK and Germany investigated the RASE approach and how its performance could be optimized. They concluded that to avoid unwanted multiple photon events one should operate with a low optical depth; however, the rephasing efficiency rises with increasing optical depth. Fortunately, by carefully shaping the spectral density of the ensemble, it should in principle be possible to satisfy both requirements and thereby realize a true single-photon source with a near-unity efficiency. Furthermore, the researchers believe that this could be implemented using currently available technology. They intend to assess how experimental imperfections, which may increase unwanted noise, affect the approach. They are also exploring the idea of creating a quantum memory by combining the outputs from two ensembles using a beam splitter.
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