Thermal effects on coherence and excitation transfer

TL;DR

This paper investigates how temperature affects quantum coherence and excitation transfer in qubit systems interacting with a common bath, revealing conditions for optimal quantum transport and coherence preservation.

Contribution

It introduces a simplified technique for solving dynamical equations and analyzes the impact of temperature on coherence and excitation transfer in qubit systems.

Findings

Incoherent initial states see increased coherence over time.

Coherent initial states lose coherence below a critical temperature.

Critical temperature depends on system size.

Abstract

To control and utilize quantum features in small scale for practical applications such as quantum transport, it is crucial to gain deep understanding of quantum characteristics of states such as coherence. Here by introducing a technique that simplifies solving the dynamical equation, we study the dynamics of coherence in a system of qubits interacting with each other through a common bath at non zero temperature. Our results demonstrate that depending on initial state, environment temperature affect coherence and excitation transfer in different ways. We show that when initial state is incoherent, as time goes on, coherence and probability of excitation transfer increase. But for coherent initial state, we find a critical value of temperature, below which system loses its coherence in time which diminishes the probability of excitation transfer. Hence in order to achieve higher value of coherence and also higher probability of excitation transfer, temperature of the bath should go beyond that critical value. Stationary coherence and probability of finding excited qubits in steady state, are discussed. We also elaborate on dependence of critical value of bath temperature on system size.