Non-Gaussian cloning of quantum coherent states is optimal.
We consider the optimal cloning of quantum coherent states with single-clone and joint fidelity as figures of merit. While the latter is maximized by a Gaussian cloner, the former is not: the optimal single-clone fidelity for a symmetric 1-to-2 cloner is 0.6826, compared to 2/3 in a Gaussian setting. This cloner can be realized with an optical parametric amplifier and certain non-Gaussian bimodal states. Finally, we show that the single-clone fidelity of the optimal 1-to-infinity cloner is 1/2. It is achieved by a Gaussian scheme and cannot be surpassed even with supplemental bound entangled states.
Cerf
N J
NJ
QUIC, Ecole Polytechnique, CP 165, Université Libre de Bruxelles, Belgium.
Krüger
O
O
Navez
P
P
Werner
R F
RF
Wolf
M M
MM