Discording power of quantum evolutions
Abstract
We introduce the discording power of a unitary transformation, which assesses its capability to produce quantum discord, and analyze in detail the generation of discord by relevant classes of two-qubit gates. Our measure is based on the Cartan decomposition of two-qubit unitaries and on evaluating the maximum discord achievable by a unitary upon acting on classical-classical states at fixed purity. We found that there exist gates which are perfect discorders for any value of purity, and that they belong to a class of operators that includes the $\sqrt{{SWAP}}. Other gates, even those universal for quantum computation, do not posses the same property: the CNOT, for example, is a perfect discorder only for states with low or unit purity, but not for intermediate values. The discording power of a two-qubit unitary also provides a generalization of the corresponding measure defined for entanglement to any value of the purity.
Cite
@article{arxiv.1208.5605,
title = {Discording power of quantum evolutions},
author = {F. Galve and F. Plastina and M. G. A. Paris and R. Zambrini},
journal= {arXiv preprint arXiv:1208.5605},
year = {2013}
}
Comments
accepted for publication in Physical Review Letters