The optimal cloning of quantum coherent states is non-Gaussian
Abstract
We consider the optimal cloning of quantum coherent states with single-clone and joint fidelity as figures of merit. Both optimal fidelities are attained for phase space translation covariant cloners. Remarkably, the joint fidelity is maximized by a Gaussian cloner, whereas the single-clone fidelity can be enhanced by non-Gaussian operations: a symmetric non-Gaussian 1-to-2 cloner can achieve a single-clone fidelity of approximately 0.6826, perceivably higher than the optimal fidelity of 2/3 in a Gaussian setting. This optimal cloner can be realized by means of an optical parametric amplifier supplemented with a particular source of non-Gaussian bimodal states. Finally, we show that the single-clone fidelity of the optimal 1-to-infinity cloner, corresponding to a measure-and-prepare scheme, cannot exceed 1/2. This value is achieved by a Gaussian scheme and cannot be surpassed even with supplemental bound entangled states.
Keywords
Cite
@article{arxiv.quant-ph/0410058,
title = {The optimal cloning of quantum coherent states is non-Gaussian},
author = {N. J. Cerf and O. Krueger and P. Navez and R. F. Werner and M. M. Wolf},
journal= {arXiv preprint arXiv:quant-ph/0410058},
year = {2007}
}
Comments
4 pages, 2 figures, revtex; changed title, extended list of authors, included optical implementation of optimal cloner