We consider the change of entanglement of formation ΔE produced by the Hadamard-CNOT circuit on a general (pure or mixed) state ρ describing a system of two qubits. We study numerically the probabilities of obtaining different values of ΔE, assuming that the initial state is randomly...

The notion of quantum discord introduced by Ollivier and Zurek [Phys. Rev. Lett 88 (2001) 017901] (see also Henderson and Vedral [J. Phys. A 34 (2001) 6899] ) has attracted increasing attention, in recent years, as an entropic quantifier of non-classical features pertaining to the correlations...

Given an arbitrary probability distribution and a nondegenerate energy spectrum, so that a mean energy U can be computed, we derive the partition function Z and the entropic functional S that satisfy the basic relation dU=TdS. The procedure is illustrated by considering examples of typical...