Discording Power of Quantum Evolutions

作者：Galve Fernando^*; Plastina Francesco; Paris Matteo G A; Zambrini Roberta

来源：Physical Review Letters, 2013, 110(1): 010501.

DOI：10.1103/PhysRevLett.110.010501

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 mu, and that they belong to a class of operators that includes the root 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. DOI:10.1103/PhysRevLett.110.010501

• 出版日期2013-1-2