Enhanced absorption microscopy with correlated photon pairs

TL;DR

This paper introduces a quantum-enhanced absorption microscopy technique using correlated photon pairs, demonstrating improved signal-to-noise ratio in imaging single-layer graphene, surpassing classical methods under certain loss conditions.

Contribution

The work proposes and experimentally demonstrates a scheme utilizing correlated photon pairs for improved optical absorption estimation in microscopy, surpassing classical illumination performance.

Findings

Achieved 1.36-fold SNR enhancement over single-photon imaging.

Demonstrated the scheme with a scanning transmission microscope.

Potential for greater improvement with multi-mode squeezed states.

Abstract

By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are fragile in noisy environments which leads to difficulties in revealing the quantum advantage. In this work, we propose a scheme to improve optical absorption estimation precision by using the correlated photon pairs from spontaneous parametric down-conversion as the illumination. This scheme performs better than clasical illumination when the loss is below a critical value. Experimentally, the scheme is demonstrated by a scanning transmission type microscope that uses correlated photon illumination. As a result, the signal-to-noise ratio (SNR) of a two-photon image shows a $1.36$-fold enhancement over that of single-photon image for a single-layer graphene with a $0.98$ transmittance. This enhancement factor will be larger when using multi-mode squeezed state as the illumination.