Entanglement dynamics of a two-qubit system coupled individually to Ohmic baths

TL;DR

This paper investigates the entanglement dynamics of two qubits each coupled to separate Ohmic baths using a variational approach, revealing finite-time disentanglement and oscillatory behaviors without common approximations.

Contribution

It applies the Davydov D1 ansatz with the Dirac-Frenkel variational method to study two-qubit entanglement dynamics beyond typical approximations.

Findings

Finite-time disentanglement in strong coupling.

Oscillatory entanglement behavior at intermediate coupling.

No use of Born-Markov or rotating-wave approximations.

Abstract

Developed originally for the Holstein polaron, the Davydov D1 ansatz is an efficient, yet extremely accurate trial state for time-dependent variation of the spin-boson model [J. Chem. Phys. 138, 084111 (2013)]. In this work, the Dirac-Frenkel time-dependent variational procedure utilizing the Davydov D1 ansatz is implemented to study entanglement dynamics of two qubits under the influence of two independent baths. The Ohmic spectral density is used without the Born-Markov approximation or the rotating-wave approximation. In the strong coupling regime finite-time disentanglement is always found to exist, while at the intermediate coupling regime, the entanglement dynamics calculated by Davydov D1 ansatz displays oscillatory behavior in addition to entanglement disappearance and revival.