Two-Qubit Spin-Boson Model in the Strong Coupling Regime: Coherence, Non-Markovianity, and Quantum Thermodynamics

TL;DR

This paper explores the complex dynamics of a two-qubit spin-boson system in the strong coupling regime, analyzing coherence, non-Markovian effects, and thermodynamic properties using advanced computational methods.

Contribution

It introduces a combined use of HEOM and RCM approaches to study non-Markovian quantum dynamics and entropy production in a strongly coupled two-qubit system.

Findings

The system exhibits non-Markovian evolution.

Quantum coherence is affected by tunneling amplitude.

Steady-state heat and spin currents depend on system parameters.

Abstract

We investigate the dynamics of a two-qubit open quantum system, in particular the two-qubit spin-boson model in the strong coupling regime, coupled to two thermal bosonic baths under non-Markovian and non-equilibrium conditions. Two complementary approaches, the Hierarchical Equations of Motion (HEOM) and Reaction Coordinate Mapping (RCM), are employed to examine various coupling regimes between the qubits and their respective baths. The dynamical features of the model and the impact of the tunneling amplitude on quantum coherence of the system are probed using the $l_1$-norm of coherence. The model is further shown to have non-Markovian evolution. The nontrivial task of calculating entropy production in the strong-coupling regime is performed using auxiliary density operators in HEOM. Motivated by the realization of a quantum thermal device in the strong-coupling regime, the non-equilibrium steady-state behavior of the system is investigated. Furthermore, the relationship between the heat and spin currents and the tunneling amplitude is probed.