Resonator-assisted single molecule quantum state detection

TL;DR

This paper introduces a novel optical detection scheme for single molecules using a high-Q resonator to achieve high-fidelity, background-free state readout without requiring a closed transition, applicable even with multiple molecules.

Contribution

It presents a new method for single-molecule detection leveraging resonator-induced transparency and analyzes its effectiveness through numerical and analytical models.

Findings

High-fidelity state readout achievable with realistic parameters

Near-unity detection fidelity for multiple molecules

Suppressed depumping rate enhances detection accuracy

Abstract

We propose a state-sensitive scheme to optically detect a single molecule without a closed transition, through strong coupling to a high-Q whispering-gallery mode high-Q resonator. A background-free signal can be obtained by detecting a molecule-induced transparency in a photon bus waveguide that is critically coupled to the resonator, with a suppressed depumping rate to other molecular states by the cooperativity parameter $C$. We numerically calculate the dynamics of the molecule-resonator coupled system using Lindblad master equations, and develop analytical solutions through the evolution of quasi-steady states in the weak-driving regime. Using Rb$_2$ triplet ground state molecules as an example, we show that high fidelity state readout can be achieved using realistic resonator parameters. We further discuss the case of multiple molecules collectively coupled to a resonator, demonstrating near-unity detection fidelity and negligible population loss.