Weak Thermal State Quadrature-Noise Shadow Imaging

TL;DR

This paper demonstrates a novel thermal quadrature-noise shadow imaging technique capable of imaging opaque objects with very low photon counts, offering advantages over classical methods and broad applicability across wavelengths.

Contribution

The work introduces a thermal QSI method that is practical, robust, and effective for low-light imaging, validated through experiments with different thermal sources and biological specimen imaging.

Findings

Thermal QSI outperforms classical differential imaging considering dark counts.

Successfully imaged biological specimens with as low as 0.03 photons per pixel.

Validated theoretical predictions with experimental results using different thermal sources.

Abstract

In this work, we theoretically and experimentally demonstrate the possibility to create an image of an opaque object using a few-photon thermal optical field. We utilize the Quadrature-Noise Shadow Imaging (QSI) technique that detects the changes in the quadrature-noise statistics of the probe beam after its interaction with an object. We show that such thermal QSI scheme has an advantage over the classical differential imaging when the effect of dark counts is considered. At the same time, the easy availability of thermal sources for any wavelength makes the method practical for broad range of applications, not accessible with, e.g. quantum squeezed light. As a proof of principle, we implement this scheme by two different light sources: a pseudo-thermal beam generated by rotating ground glass (RGG) method and a thermal beam generated by Four-Wave Mixing (FWM) method. The RGG method shows simplicity and robustness of QSI scheme while the FWM method validates theoretical signal-to-noise ratio predictions. Finally, we demonstrate low-light imaging abilities with QSI by imaging a biological specimen on a CCD camera, detecting as low as 0.03 photons on average per pixel per 1.7 microseconds exposure.