Coherent excitation-energy transfer and quantum entanglement in a dimer

TL;DR

This paper investigates how energy detuning and bath temperatures influence coherent energy transfer and quantum entanglement in a dimer system modeled by two two-level systems, revealing temperature-dependent effects on transfer probability and entanglement.

Contribution

It provides a detailed analysis of the effects of energy detuning and heat bath temperatures on energy transfer and entanglement in a dimer, highlighting conditions for optimal quantum coherence.

Findings

Energy detuning affects transfer probability at low temperatures.

Higher bath temperatures reduce steady-state entanglement.

Transfer probability is insensitive to temperature differences between baths.

Abstract

We study coherent energy transfer of a single excitation and quantum entanglement in a dimer, which consists of a donor and an acceptor modeled by two two-level systems. Between the donor and the acceptor, there exists a dipole-dipole interaction, which provides the physical mechanism for coherent energy transfer and entanglement generation. The donor and the acceptor couple to two independent heat baths with diagonal couplings that do not dissipate the energy of the non-coupling dimer. Special attention is paid to the effect on single-excitation energy transfer and entanglement generation of the energy detuning between the donor and the acceptor and the temperatures of the two heat baths. It is found that, the probability for single-excitation energy transfer largely depends on the energy detuning in the low temperature limit. Concretely, the positive and negative energy detunings can increase and decrease the probability at the steady state, respectively. In the high temperature limit, however, the effect of the energy detuning on the probability is neglectably small. We also find that the probability is neglectably dependent on the bath temperature difference of the two heat baths. In addition, it is found that quantum entanglement can be generated in the process of coherent energy transfer. As the bath temperature increases, the generated steady state entanglement decreases. For a given bath temperature, the steady-state entanglement decreases with the increasing of the absolute value of the energy detuning.