Year: 2013
Type: article
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 find that there exist gates which are perfect discorders for any value of purity μ, and that they belong to a class of operators that includes the sqrt[SWAP]. Other gates, even those universal for quantum computation, do not possess 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.
Source: Physical Review Letters
Institutions: Institute for Cross-Disciplinary Physics and Complex Systems, Universitat de les Illes Balears, Istituto Nazionale di Fisica Nucleare, Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Cosenza, University of Calabria, University of Milan, National Interuniversity Consortium for the Physical Sciences of Matter
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2035964917