The Quantum Optics Group
at the Hebrew University of Jerusalem
Projection of two biphoton qutrits onto a maximally entangled state

Bell state measurements, in which two quantum bits are projected onto a maximally entangled state, are essential operations in quantum information science; they stand in the heart of protocols such as quantum teleportation [1, 2] and entanglement swapping [3].

All of the projection schemes to date utilized two quantum bits – qubits. We have proposed and experimentally demonstrated the projection of two quantum three state systems (qutrits) onto a maximally entangled state. These qutrits are represented by the polarization of pairs of indistinguishable photons, called biphotons.

We have recently shown that biphoton qutrits improve the security and efficiency of quantum key distribution [4]. Moreover, qutrits can also enhance the performance of quantum communication protocols [5].

Our suggested Bell projection can enable the realization of qutrit teleportation, entanglement swapping and other such extensions for quantum information protocols.

For more details on our work, see Ref. [6].


[1]     C.H. Bennett, G. Brassard C. Crépeau,  R. Jozsa, A. Peres and W.K. Wootters, “Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels“,  Phys. Rev. Lett. 70, 1895-1899 (1993).

[2]     D. Bouwmeester, J.W. Pan, K. Mattle, M. Eibl, H. Weinfurter and A. Zeilinger, “Experimental quantum  teleportation”, Nature (London) 390, 575-579 (1997).

[3]     J.W. Pan, D. Bouwmeester, H. Weinfurter and A. Zeilinger, “Experimental entanglement swapping: entangling photons that never interacted”, Phys. Rev. Lett. 80, 3891-3894 (1998).

[4]     I. Bregman, D. Aharonov, M. Ben-Or and H.S. Eisenberg, “Simple and secure quantum key distribution with biphotons”, Phys. Rev. A 77, 050301 (2008).

[5]     Č. Brukner , M. Żukowski and Anton Zeilinger, “Quantum communication complexity protocol with two entangled qutrits”, Phys. Rev. Lett. 89, 197901 (2002).

[6]     A. Halevy, E. Megidish, T. Shacham, L. Dovrat  and H.S. Eisenberg., “Projection of two biphoton qutrits onto a maximally entangled state”,         arXiv:1011.6202 [quant-ph].