|Record Storage Time for Single Quantum Memory|
PAN Jianwei and his coworker ZHAO Bo, CHEN Yuao et al at Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China published their latest findings in February 1, 2009 online issue of journal Nature Physics, reporting the realization of the storage of long-lived quantum memories. In collaboration with the counterparts from Germany and Austria, the study team headed by PAN made an experiment to store quantum state using atomic state, while prolonging spin waves. They have for the first time in the world extended the storage time of single quantum memories to the order of a millisecond, two orders of magnitude longer than reported so far, bringing practical long-distance quantum-communication networks a step closer. Researchers identified and isolated the distinct mechanisms responsible for the decoherence of spin waves in atomic-ensemble-based quantum memories. They found that the dephasing of spin waves caused by atomic movement also makes a major factor causing short quantum memories, in addition to the impact of magnetic field. Unfortunately, the decoherence of spin waves have been ignored in the past studies. As a result, researchers made an attempt to store quantum state using magnetic-field-insensitive states, or so -called clock states, and succeeded in extending the storage time of the quantum memory to 1 millisecond, or 300km for light traveling in air or through optic-fibers.