Anti-symmetrization reveals hidden entanglement

Alessandro Fedrizzi (1, 2) , Thomas Herbst (1) , Markus Aspelmeyer (1) , Marco Barbieri (3, 2) , Thomas Jennewein (2, 1) , Anton Zeilinger (1, 4)

1 Institute for Quantum Optics and Quantum Information
2 Department of Physics and Centre for Quantum Computer Technology
3 Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique
4 Faculty of Physics [Vienna]

Two-photon anti-bunching at a beamsplitter is only possible if the photons are entangled in a specific state, anti-symmetric in the spatial modes. Thus, observation of anti-bunching is an indication of entanglement in a degree of freedom which might not be easily accessible in an experiment. We experimentally demonstrate this concept in the case of the interference of two frequency entangled photons with continuous frequency detunings. The principle of anti-symmetrisation of the spatial part of a wavefunction and subsequent detection of hidden entanglement via anti-bunching at a beamsplitter may facilitate the observation of entanglement in other systems, like atomic ensembles or Bose-Einstein condensates. The analogue for fermionic systems would be to observe bunching.

Domains: Quantum Physics [quant-ph]

Alessandro Fedrizzi, Thomas Herbst, Markus Aspelmeyer, Marco Barbieri, Thomas Jennewein, et al.. Anti-symmetrization reveals hidden entanglement. New Journal of Physics, 2009, 11, pp.103052. ⟨10.1088/1367-2630/11/10/103052⟩. ⟨hal-00569530⟩