# Spin State Dynamics in a Bichromatic Microwave Field: Role of Bright and Dark States in coupling with Reservoir

## TL;DR

This paper investigates how a bichromatic microwave field influences spin state dynamics, revealing complex resonance behaviors linked to bright and dark states and their interactions with the environment.

## Contribution

It introduces a detailed analysis of spin state interactions under bichromatic excitation, highlighting the roles of bright and dark states in resonance behavior and decoherence.

## Key findings

- Nested magnetic resonances with power-dependent widths
- Field-induced stabilization of certain resonances
- Light-induced narrowing of composite resonances

## Abstract

Driving an open spin system by two strong, nearly degenerate fields enables addressing populations of individual spin states, characterisation of their interaction with thermal bath, and measurements of their relaxation/decoherence rates. With such addressing we observe nested magnetic resonances having nontrivial dependence on microwave field intensity: while the width of one of the resonances undergoes a strong power broadening, the other one exhibits a peculiar field-induced stabilization. We also observe light-induced narrowing of such composite resonances. The observations are explained by the dynamics of bright and dark superposition states and their interaction with reservoir.