Suppression of Collisional Decoherence by Dynamical Decoupling

Abstract

As was already mentioned, cold atomic ensembles can be used as an interface between matter and photonic qubits in quantum networks, and in recent years vast experimental advances in this direction have been reported [35, 53–57]. The effect of collisional fluctuations was analyzed in the previous chapters and the decoherence it induces is well understood. Though fluctuations at low frequencies can be overcome by a single population inverting pulse - the celebrated coherence echo technique [58, 59], as the collision rate increases this is no longer possible due to higher frequency components. Dynamical decoupling (DD) theories generalize this technique to multi-pulse sequences by harnessing symmetry properties of the coupling Hamiltonian [60, 61, 62, 7, 8]. Though DD was demonstrated in several experiments [63–68], its use with atomic ensembles remains unexplored to date. In this chapter we study experimentally DD in a dense cold atomic ensemble and report on a substantial suppression of collisional decoherence.