Evolution of entanglement within classical light states
  We investigate the evolution of quantum correlations over the lifetime of a multi-photon state. Measurements reveal time-dependent oscillations of the entanglement fidelity for photon pairs created by a single semiconductor quantum dot. The oscillations are attributed to the phase acquired in the intermediate, non-degenerate, exciton-photon state and are consistent with simulations. We conclude that emission of photon pairs by a typical quantum dot with finite polarisation splitting is in fact entangled in a time-evolving state, and not classically correlated as previously regarded. 
R. Mark Stevenson, Andrew J. Hudson, Anthony J. Bennett, Robert J.   Young, Christine A. Nicoll, David A. Ritchie, and Andre...