Two-photon interference without bunching two photons

We report an experiment which conclusively demonstrates that the two-photon entangled state interference cannot be pictured as the overlap and 'bunching' of two individual photons on a beamsplitter. We also demonstrate that photon 'bunching' does not occur if the two-photon Feynman amplitudes are distinguishable, even though individual photons do overlap on a beamsplitter. (C) 2003 Elsevier B.V. All rights reserved.