Quantum-enhanced absorption spectroscopy

TL;DR

This paper demonstrates sub-shot-noise absorption spectroscopy using correlated photon pairs, achieving higher precision with fewer photons compared to traditional laser-based methods, especially in biological sample analysis.

Contribution

It introduces a quantum-enhanced spectroscopy technique utilizing correlated photon pairs to surpass shot-noise limits in absorption measurements.

Findings

Achieved sub-shot-noise absorption spectra with correlated photons.

Fewer photons needed for a given precision compared to ideal laser sources.

Successfully distinguished biological samples with higher accuracy.

Abstract

Absorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use wavelength-correlated and tuneable photon pairs to demonstrate sub-shot-noise absorption spectroscopy. We measure the absorption spectra of spectrally-similar biological samples---oxyhaemoglobin and carboxyhaemoglobin---and show that obtaining a given precision in resolution requires fewer heralded single probe photons compared to using an ideal laser.