Maximization of thermal entanglement of arbitrarily interacting two qubits

TL;DR

This paper studies how to maximize thermal entanglement in two interacting qubits by tuning local Hamiltonians, revealing temperature-dependent behaviors and phase transition characteristics.

Contribution

It proves the form of the optimal local Hamiltonian for maximizing entanglement and analyzes its temperature-dependent decay and phase transition properties.

Findings

Optimal local Hamiltonian form is temperature-independent.

Thermal entanglement decays as 1/(T log T) at high temperatures.

Discontinuous change in second derivative at phase boundary.

Abstract

We investigate the thermal entanglement of interacting two qubits. We maximize it by tuning a local Hamiltonian under a given interaction Hamiltonian. We prove that the optimizing local Hamiltonian takes a simple form which dose not depend on the temperature and that the corresponding optimized thermal entanglement decays as $1/(T log T)$ at high temperatures. We also find that at low temperatures the thermal entanglement is maximum without any local Hamiltonians and that the second derivative of the maximized thermal entanglement changes discontinuously at the boundary between the high- and low-temperature phases.