Weak Thermal State Quadrature-Noise Shadow Imaging

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 distinct methods: first, with pseudo-thermal light generated by rotating ground glass (RGG) method and second, with 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 just 0.006 photons per pixel on average.

Low‐Light Shadow Imaging Using Quadrature‐Noise Detection with a Camera

“…Our homodynelike detection scheme allows elimination of the detrimental effects of the camera's dark noise and, potentially, is immune to the classical background illumination while keeping the probing intensity low. This approach is particularly attractive for applications requiring weak illumination since the squeezed vacuum inherently has very few photons illuminating the object, and can even be expanded to other noisy, non-coherent states (e.g., the thermal state [11] ).…”