Controllable dynamics of two separate qubits in Bell states

TL;DR

This paper investigates how the entanglement and fidelity of two separate qubits in Bell states can be controlled by tuning parameters of a spin-bath, revealing dynamics independent of initial Bell states.

Contribution

It demonstrates controllable entanglement and fidelity dynamics in two qubits influenced by a spin-bath, with analysis for both infinite and finite bath sizes.

Findings

Concurrence dynamics are independent of initial Bell states.

Fidelity dynamics split into two distinct groups.

Control achieved via bath parameters like anisotropy, temperature, and coupling.

Abstract

The dynamics of entanglement and fidelity for a subsystem of two separate spin-1/2 qubits prepared in Bell states is investigated. One of the subsystem qubit labelled $A$ is under the influence of a Heisenberg XY spin-bath, while another one labelled $B$ is uncoupled with that. We discuss two cases: (i) the number of bath spins $N\to\infty$; (ii) $N$ is finite: N=40. In both cases, the bath is initially prepared in a thermal equilibrium state. It is shown that the time dependence of the concurrence and the fidelity of the two subsystem qubits can be controlled by tuning the parameters of the spin-bath, such as the anisotropic parameter, the temperature and the coupling strength with qubit $A$. It is interesting to find the dynamics of the concurrence is independent of four different initial Bell states and that of the fidelity is divided into two groups.