Enhancement of Quantum Excitation Transport by Photonic Nonreciprocity

TL;DR

This paper demonstrates that breaking electromagnetic reciprocity in photonic environments significantly enhances quantum excitation transport efficiency between two-level emitters, with potential applications in quantum information and biological sensing.

Contribution

It provides a detailed analytical explanation of how nonreciprocal photonic media improve excitation transfer, including a practical example with plasmonic waveguides.

Findings

Breaking reciprocity increases cooperative decay rates.

Nonreciprocal systems can surpass spontaneous decay limits.

Driving DC current enhances photon-mediated energy transfer.

Abstract

Enhanced interaction between two two-level emitters (e.g., atoms) by nonreciprocal photonic media can be of benefit to broad areas, from quantum information science to biological detection. Here we provide a detailed analysis on why nonreciprocal photon-mediated interaction enhances inter-atomic excitation transport efficiency. We investigate a system consisting of two two-level emitters embedded in a generic photonic environment. By comparing symmetric and asymmetric photon-exchange, we analytically show that breaking electromagnetic reciprocity makes it possible for the cooperative decay rate to exceed the spontaneous decay rate even in a translation-invariant homogeneous system. This means that the excitation of an emitter must decay mostly into the other emitter rather than leaking and dissipating into the reservoir photonic modes. We also provide an example where a chain of two-level emitters dominantly interact via the reciprocal modes of a plasmonic waveguide. We then show that breaking reciprocity in such a system via driving a DC current through the plasmonic material can drastically increase the probability of photon emission from one emitter to another, leading to an order-of-magnitude enhancement in quantum energy-transport efficiency.