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 , 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.
Discording Power of Quantum Evolutions / Galve, F; Plastina, Francesco; Paris M. G., A; Zambrini, R.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 110(2013), pp. 010501.010501-1-010501.010501-5.
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Titolo: | Discording Power of Quantum Evolutions |
Autori: | |
Data di pubblicazione: | 2013 |
Rivista: | |
Citazione: | Discording Power of Quantum Evolutions / Galve, F; Plastina, Francesco; Paris M. G., A; Zambrini, R.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 110(2013), pp. 010501.010501-1-010501.010501-5. |
Handle: | http://hdl.handle.net/20.500.11770/133728 |
Appare nelle tipologie: | 1.1 Articolo in rivista |