Quantum dynamics of a driven two-level molecule with variable dephasing

TL;DR

This study investigates how variable dephasing rates affect the quantum dynamics of a driven two-level molecule, combining experimental measurements with theoretical modeling to understand the influence of environmental interactions.

Contribution

It provides experimental data on temperature-dependent dephasing and validates the optical Bloch equations across different regimes, highlighting limitations of existing approximations.

Findings

Dephasing rate varies with temperature and affects quantum dynamics.

Optical Bloch equations accurately model the system across parameters.

Limitations of approximate models for $g^{(2)}( au)$ are discussed.

Abstract

The longitudinal ($\Gamma_1$) and transverse ($\Gamma_2$) decay rates of a two-level quantum system have profound influence on its evolution. Atomic systems with $\Gamma_2=\tfrac{1}{2}\Gamma_1$ have been studied extensively, but with the rise of solid-state quantum devices it is also important to consider the effect of stronger transverse relaxation due to interactions with the solid environment. Here we study the quantum dynamics of a single organic dye molecule driven by a laser. We measure the variation of $\Gamma_2$ with temperature and determine the activation energy for thermal dephasing of the optical dipole. Then we measure the second-order correlation function $g^{(2)}(\tau)$ of the light emitted by the molecule for various ratios $\Gamma_2/\Gamma_1$ and saturation parameters $S$. We show that the general solution to the optical Bloch equations accurately describes the observed quantum dynamics over a wide range of these parameters, and we discuss the limitations of the various approximate expressions for $g^{(2)}(\tau)$ that appear in the literature.