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Optimal quantum cloning of orbital angular momentum photon qubits through Hong–Ou–Mandel coalescence

2009; Nature Portfolio; Volume: 3; Issue: 12 Linguagem: Inglês

10.1038/nphoton.2009.214

1749-4893

Eleonora Nagali, Linda Sansoni, Fabio Sciarrino, Francesco De Martini, Lorenzo Marrucci, Bruno Piccirillo, Ebrahim Karimi, Enrico Santamato,

Optical Polarization and Ellipsometry

The orbital angular momentum (OAM) of light, associated with a helical structure of the wavefunction, has great potential in quantum photonics, as it allows a higher dimensional quantum space to be attached to each photon1,2. Hitherto, however, the use of OAM has been hindered by difficulties in its manipulation. Here, by making use of the recently demonstrated spin-OAM information transfer tools3,4, we report the first observation of the Hong–Ou–Mandel coalescence5 of two incoming photons having non-zero OAM into the same outgoing mode of a beamsplitter. The coalescence can be switched on and off by varying the input OAM state of the photons. Such an effect has then been used to carry out the 1 → 2 universal optimal quantum cloning of OAM-encoded qubits6,7,8, using the symmetrization technique already developed for polarization9,10. These results are shown to be scalable to quantum spaces of arbitrary dimensions, even combining different degrees of freedom of the photons. The first observation of the Hong–Ou–Mandel coalescence of photons with orbital angular momentum (OAM) is demonstrated, and this is exploited for optimal quantum cloning of OAM-encoded qubits. OAM states may function as units of quantum information in higher-dimensional space and allow increased information content per photon.