Abstract
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.
- Received 31 March 2011
DOI:https://doi.org/10.1103/PhysRevLett.106.243602
© 2011 American Physical Society
Synopsis
Single photons obey the speed limits
Published 16 June 2011
Observations of single photons traveling through cold atomic gases confirm that information can only travel as fast as the speed of light.
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