Shanchao Zhang, J.F. Chen, Chang Liu, M.M.T Loy, G.K.L. Wong, Shengwang Du
We report the direct observation of optical precursors of heralded single photons with step- and square-modulated wave packets passing through cold atoms. Using electromagnetically induced transparency and the slow-light effect, we separate the single-photon precursor, which always travels at the speed of light in vacuum, from its delayed main wave packet. In the two-level superluminal medium, our result suggests that the causality holds for a single photon.
Thursday, July 21, 2011
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