Interferometric Mass Photometry at the Quantum Limit of Sensitivity

TL;DR

This paper introduces a quantum-limited interferometric imaging system that enhances particle measurement sensitivity beyond conventional methods by utilizing a Michelson interferometer and quantum state analysis.

Contribution

It presents a novel optical setup combining a Michelson interferometer with quantum state evaluation to reach the quantum Cramér-Rao bound in particle mass and phase measurements.

Findings

Achieves quantum Cramér-Rao bound for sensitivity

Outperforms conventional iSCAT in mass and phase estimation

Effective with various quantum states including coherent states

Abstract

We present an innovative optical imaging system for measuring parameters of a small particle such as a macromolecule or nanoparticle at the quantum limit of sensitivity. In comparison to the conventional confocal interferometric scattering (iSCAT) approach, our setup adds a second arm to form a Michelson interferometer that allows us to tune a relative phase. We evaluate the quantum Cram\'er-Rao bound (QCRB) for different quantum states, including single-mode coherent states, multi-frequency coherent states, and phase-averaged coherent states. Our results show that the proposed setup can achieve the QCRB of sensitivity and outperform iSCAT for all considered quantum states for mass and phase estimation of a particle.