The Volume of Two-Qubit States by Information Geometry

The Volume of Two-Qubit States by Information Geometry

Using the information geometry approach, we determine the volume of the set of two-qubit states with maximally disordered subsystems. Particular attention is devoted to the behavior of the volume of sub-manifolds of separable and entangled states with fixed purity. We show that the usage of the classical Fisher metric on phase space probability representation of quantum states gives the same qu...

Decoherence effects on quantum Fisher information of multi-qubit W states

Quantum fisher information of a parameter characterizing the sensitivity of a state with respect to parameter changes. In this paper, we study the quantum fisher information of the W state for four, five, six and seven particles in decoherence channels, such as amplitude damping, phase damping and depolarizing channel. Using Krauss operators for decoherence channels components, we investigate t...

Nonseparability and steerability of two-qubit states from the geometry of steering outcomes

Purification of two-qubit mixed states

is a frequent choice. However, in practical situations decoherence makes pure states evolve into mixed states and reduces its entanglement. Therefore, in the last years much work has been devoted to understand under which conditions the entanglement that has been lost can be recovered using local operations and classical communication (LOCC). In general there are two frameworks under which the ...

Quantum Discord and Geometry for a Class of Two-qubit States

We study the level surfaces of quantum discord for a class of two-qubit states with parallel nonzero Bloch vectors. The dynamic behavior of quantum discord under decoherence is investigated. It is shown that a class of X states has sudden transition between classical and quantum correlations under decoherence. Our results include the ones in [Phys. Rev. Lett. 105. 150501] as a special case and ...