Thermal quantum correlations in a three-qubit spin chain under an in-homogeneous magnetic field

Abstract

The thermal quantum correlations of a three-qubit spin chain of XY type under an in-homogeneous magnetic field have been investigated, where by considering magnetic fields with different magnitudes [Formula: see text], [Formula: see text] and [Formula: see text] for each spin, the quantum correlations between the adjacent and the non-adjacent qubits (spins) have been studied. For this purpose, the concurrence as an entanglement quantifier and the trace distance discord as a discord-like quantifier have been computed for the corresponding bipartite subsystems with the reduced density matrices [Formula: see text], [Formula: see text] and [Formula: see text]. The differences between the concurrence and the trace distance discord, are explained in detail. Their dependence on the parameters of the uniform magnetic field [Formula: see text], the temperature [Formula: see text], and the in-homogeneity parameter [Formula: see text] is discussed so that the thermal correlation decreases by increasing the mentioned parameters. Also, the results show that by changing and controlling the parameters [Formula: see text], [Formula: see text] and [Formula: see text], especially the in-homogeneous magnetic field [Formula: see text], it is possible that the correlation value between non-adjacent spins, i.e. [Formula: see text] can be reached to a greater value than the thermal correlations between adjacent spins, i.e. [Formula: see text] and [Formula: see text]. Moreover, it is shown that the trace distance [Formula: see text] between the non-adjacent spins has always a lower value than those of the adjacent spins [Formula: see text] and [Formula: see text]. Finally, the results show that in-homogeneous magnetic field b can be effective for improving thermal quantum correlation.