Precise quantum tomography of photon pairs with entangled orbital angular momentum

B. Jack, J. Leach, H. Ritsch, S.M. Barnett, M.J. Padgett, S. Franke-Arnold

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We report a high fidelity tomographic reconstruction of the quantum state of photon pairs generated by parametric down-conversion with orbital angular momentum (OAM) entanglement. Our tomography method allows us to estimate an upper and lower bound for the entanglement between the down-converted photons. We investigate the two-dimensional state subspace defined by the OAM states ± and superpositions thereof, with =1, 2, ..., 30. We find that the reconstructed density matrix, even for OAMs up to around =20, is close to that of a maximally entangled Bell state with a fidelity in the range between F=0.979 and F=0.814. This demonstrates that, although the single count-rate diminishes with increasing , entanglement persists in a large dimensional state space.
Original languageEnglish
Article number103024
Number of pages12
JournalNew Journal of Physics
Publication statusPublished - 12 Oct 2009


  • quantum tomography
  • photon pairs
  • orbital angular momentum
  • parametric down-conversion
  • entanglement


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