Efficient single photon detection with cold atoms in hollow fiber

Cold atoms confined inside a hollow core photonic crystal fiber are a promising medium for studying nonlinear optical interactions at extremely low light levels. For instance, we demonstrated in recent experiments how such an atomic ensemble consisting of $\sim10^3$ laser cooled $^{87}Rb$ atoms results in an optically dense medium whose transparency can be controlled with pulses containing just a few hundred photons [1]. Here, we describe how this medium can be used for high efficiency detection of single stored excitations. This in turn allows for non-destructive detection of single photons with near unity probability, which for example could greatly enhance the efficiency of the DLCZ-scheme for quantum repeaters. We also discuss recent improvements of the atom loading scheme to increase the optical depth of the atomic medium inside the hollow core fiber. [1] M.~Bajcsy, S.~Hofferberth, V.~Balic, T.~Peyronel, M.~Hafezi, A.~S.~Zibrov, V.~Vuletic, M.~D.~Lukin, Efficient all-optical switching using slow light within a hollow fiber, arXiv:0901.0336 (2009)