Fundamental efficiency bound for coherent energy transfer in nanophotonics

TL;DR

This paper establishes a fundamental quantum limit on energy transfer efficiency in nanophotonics, linking it to spontaneous emission rates, and suggests control of these rates as a new design principle, with potential experimental validation.

Contribution

It derives a universal efficiency bound for energy transfer in nanophotonics and introduces a novel approach to enhance efficiency by controlling spontaneous emission rates.

Findings

Derived a fundamental efficiency bound based on spontaneous emission rates.

Proposed using mirrors and dipole orientation to surpass current efficiency limits.

Showed quantum coherence is not necessary to reach the efficiency bound.

Abstract

We derive a unified quantum theory of coherent and incoherent energy transfer between two atoms (donor and acceptor) valid in arbitrary Markovian nanophotonic environments. Our theory predicts a fundamental bound $\eta_{max} = \frac{\gamma_a}{\gamma_d + \gamma_a}$ for energy transfer efficiency arising from the spontaneous emission rates $\gamma_{d}$ and $\gamma_a$ of the donor and acceptor. We propose the control of the acceptor spontaneous emission rate as a new design principle for enhancing energy transfer efficiency. We predict an experiment using mirrors to enhance the efficiency bound by exploiting the dipole orientations of the donor and acceptor. Of fundamental interest, we show that while quantum coherence implies the ultimate efficiency bound has been reached, reaching the ultimate efficiency does not require quantum coherence. Our work paves the way towards nanophotonic analogues of efficiency enhancing environments known in quantum biological systems.