Campbell, G.Hosseini, M.Sparkes, B.Lam, P.Buchler, B.2017-06-012017-06-012012New Journal of Physics, 2012; 14(3):033022-1-033022-101367-26301367-2630http://hdl.handle.net/2440/105588Published 13 March 2012We present experimental observations of interference between an atomic spin coherence and an optical field in a Λ-type gradient echo memory. The interference is mediated by a strong classical field that couples a weak probe field to the atomic coherence through a resonant Raman transition. Interference can be observed between a prepared spin coherence and another propagating optical field, or between multiple Λ transitions driving a single-spin coherence. Our scheme can behave as a controllable time-delayed beamsplitter with dynamically tuneable splitting ratio and allows, in principle, for unity interference visibility.en© IOP Publishing Ltd and Deutsche Physikalische GesellschaftJournal article003006848710.1088/1367-2630/14/3/0330220003023406000062-s2.0-84859622505348786Sparkes, B. [0000-0002-9370-2006]