Tuning Spectral Properties of Individual and Multiple Quantum Emitters in Noisy Environments

TL;DR

This paper demonstrates that applying periodic finite-width pulses can effectively refocus and protect the spectral properties of quantum emitters in noisy, fluctuating environments, enhancing their coherence and interference capabilities.

Contribution

It introduces a control protocol using finite-width pulse sequences to mitigate spectral diffusion and inhomogeneous broadening in quantum emitters affected by noisy environments.

Findings

Pulse sequences refocus emission spectrum onto the carrier frequency.

Two-photon interference efficiency is improved with pulse control.

Inhomogeneous broadening in ensembles can be narrowed to a single emitter linewidth.

Abstract

A quantum emitter in a dynamic environment may have its energy levels drift uncontrollably in time with the fluctuating bath. This can result in an emission/absorption spectrum that is spread over a broad range of frequencies and presents a challenging hurdle for various applications. We consider a quantum emitter in an environment that alters the energy levels so that the emission frequency is represented by a Gaussian random distribution around a given mean value with given standard deviation and correlation time. We study the emission spectrum of this system when it is placed under the influence of a periodic sequence of finite width $\pi$ pulses. We show that this external field protocol can effectively overcome spectral diffusion in this system by refocusing the bulk of the emission spectrum onto the pulse carrier frequency. We further consider two such emitters in different noisy environments and find that the two-photon interference operation can be made efficient by the sequence of finite width pulses applied on both systems. Finally, we show that an ensemble of nominally similar emitters, each with its different environment, and thus randomly shifted emission frequency, can have its overall emission spectrum that would otherwise be inhomogeneously broadened according to the random distribution, refocused onto a lineshape with a well-defined central peak that has the linewidth of an individual isolated non-noisy emitter. These results demonstrate for this specific model of noisy environments, the protection of spectral properties by an external control protocol here represented by a periodic sequence of finite width pulses.