Microscopy with heralded Fock states

TL;DR

This paper explores quantum light microscopy using heralded Fock states, providing analytical formulas and demonstrating how to improve resolution and signal-to-noise ratio through mode shaping and quantum properties.

Contribution

It introduces analytical models for spatial mode tracking in quantum microscopy with heralded single photons and discusses practical methods to enhance resolution and reduce photon loss.

Findings

Diffraction limit can be approached with quantum light.

Spatial resolution can be manipulated via mode profile preparation.

Photon loss can be alleviated while increasing signal-to-noise ratio.

Abstract

We consider a microscopy setting where quantum light is used for illumination. Spontaneous parametric down conversion (SPDC) is used as a source of a heralded single photon, which is quantum light prepared in a Fock state. We present analytical formulas for the spatial mode tracking along with the heralded and non-heralded mode widths. The obtained analytical results are supported by numerical calculations and the following discussion taking into account realistic setup parameters such as finite-size optics and finite-size single-photon detectors. This allows us to observe that the diffraction limit can be approached with simultaneous alleviation of the photon loss leading to increased signal-to-noise ratio - a factor limiting practical applications of quantum light. Additionally, it is shown that the spatial resolution can be manipulated by carefully preparing the amplitude and phase of the spatial mode profile of the single photon at the input to the microscope objective. Here, the spatial entanglement of the biphoton wavefunction or adaptive optics can be applied for spatial mode shaping. Analytical dependencies between the incident and focused spatial mode profiles parameters are provided.