Stuttgart 2012 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 69: Quanteninformation: Kommunikation
Q 69.1: Vortrag
Freitag, 16. März 2012, 14:00–14:15, V38.04
High-fidelity polarisation storage in a broadband quantum memory — Duncan G. England1, Patrick S. Michelberger1, •Tessa F. M. Champion1, Klaus F. Reim1, Ka Chung Lee1, Michael R. Sprague1, Xian-Min Jin1,2, Nathan K. Langford1, William S. Kolthammer1, Joshua Nunn1, and Ian A. Walmsley1 — 1Department of Physics, University of Oxford — 2Centre for Quantum Technologies, National University of Singapore
Quantum memories are an essential requirement for the efficient distribution of quantum information across large-scale quantum networks. Coherent storage and on-demand retrieval of polarisation-encoded information is demonstrated for the first time in a broadband quantum memory. Based on the far-off-resonant Raman interaction, our memory protocol allows storage of sub-nanosecond light pulses in a room-temperature caesium vapour. The polarisation of weak coherent states is stored in a dual-rail Raman memory inside a polarisation interferometer. Full process tomography of the system reveals process fidelities of up to 97±1% for the storage and retrieval processes. For longer storage times, the process fidelities remain high despite decreased memory efficiencies. The memory’s ability to preserve polarisation information is therefore largely insensitive to loss. In particular, a process fidelity of 86±4% is found for a storage time of 1.5µs, which is 5000 times longer than the pulse duration itself. Hence, high-fidelity storage is combined with a large time-bandwidth product in a technically simple room-temperature device. This demonstrates the Raman memory’s suitability for integration into large-scale quantum networks.