Quantum limits to resolution and discrimination of spontaneous emission lifetimes

TL;DR

This paper explores the fundamental quantum limits of resolving and discriminating spontaneous emission lifetimes, revealing how quantum measurement strategies can surpass classical approaches in optical emitter analysis.

Contribution

It introduces quantum-inspired measurement schemes that overcome the classical Rayleigh's Curse in lifetime resolution and discrimination tasks.

Findings

Quantum measurement schemes outperform direct measurement in lifetime discrimination.

Rayleigh's Curse analog affects lifetime resolution with overlapping decays.

Quantum analysis reveals significant information gains in opto-molecular metrology.

Abstract

In this work we investigate the quantum information theoretical limits to several tasks related to lifetime estimation and discrimination of a two-level spontaneous optical emitter. We focus in particular on the model problem of resolving two mutually incoherent exponential decays with highly overlapping temporal probability profiles. Mirroring recent work on quantum-inspired super-resolution of point emitters, we find that direct lifetime measurement suffers from an analogue of "Rayleigh's Curse" when the time constants of the two decay channels approach one another. We propose alternative measurement schemes that circumvent this limit, and also demonstrate superiority to direct measurement for a related binary hypothesis test. Our findings add to a growing list of examples in which a quantum analysis uncovers significant information gains for certain tasks in opto-molecular metrology that do not rely on multiphoton interference, but evidently do benefit from a more thorough exploitation of the coherence properties of single photons.