Experimental Quantum Cloning of Single Photons
Antía Lamas-Linares,1*
Christoph Simon,1
John C. Howell,1
Dik Bouwmeester12
Although perfect copying of unknown quantum systems is forbidden by
the laws of quantum mechanics, approximate cloning is possible. A
natural way of realizing quantum cloning of photons is by stimulated
emission. In this context, the fundamental quantum limit to the quality
of the clones is imposed by the unavoidable presence of spontaneous
emission. In our experiment, a single input photon stimulates the
emission of additional photons from a source on the basis of parametric
down-conversion. This leads to the production of quantum clones with
near-optimal fidelity. We also demonstrate universality of the copying
procedure by showing that the same fidelity is achieved for arbitrary
input states.
1 Centre for Quantum Computation, University of
Oxford, Parks Road, Oxford OX1 3PU, UK.
2 Department
of Physics, University of California at Santa Barbara, Santa Barbara,
CA 93106, USA.
*
To whom correspondence should be addressed. E-mail:
a.lamas{at}qubit.org
Present address: Department of Physics and Astronomy,
University of Rochester, Rochester, NY14627, USA.
