Quantum-enhanced microscopy with binary-outcome photon counting

TL;DR

This paper addresses phase sensitivity divergence in quantum-enhanced microscopy using N-photon states, proposing two schemes to eliminate singularities and improve image quality with high photon number states.

Contribution

It introduces two novel methods to remove phase sensitivity singularities in quantum microscopy using twin-Fock states, enhancing imaging performance.

Findings

Singularity occurs due to experimental imperfections in twin-Fock state microscopy.

Two schemes successfully eliminate phase sensitivity divergence.

Methods are applicable to any binary-outcome measurement in quantum microscopy.

Abstract

Polarized light microscopy using path-entangled $N$-photon states (i.e., the N00N states) has been demonstrated to surpass the shot-noise limit at very low light illumination. However, the microscopy images suffer from divergence of phase sensitivity, which inevitably reduces the image quality. Here, we show that due to experimental imperfections, such a singularity also takes place in the microscopy that uses twin-Fock states of light for illumination. We propose two schemes to completely eliminate this singularity: (i) locking the phase shift sensed by the beams at the optimal working point, by using a spatially dependent offset phase; (ii) a combination of two binary-outcome photon counting measurements, one with a fixed offset phase and the other without any offset phase. Our observations remain valid for any kind of binary-outcome measurement and may open the way for quantum-enhanced microscopy with high $N$ photon states.