Diffraction of correlated biphotons through transparent samples

TL;DR

This paper demonstrates that correlated biphotons exhibit diffraction-like behavior when passing through transparent samples, enabling quantum-enhanced, non-interferometric phase imaging with improved contrast.

Contribution

It introduces a novel method to analyze biphoton diffraction effects and reconstruct phase structures using correlation images and event-based cameras.

Findings

Correlation images reveal sample phase structures.

Enhanced contrast in phase retrieval due to biphoton correlations.

Experimental validation with event-based camera detection.

Abstract

Two-photon states generated through degenerate spontaneous parametric down-conversion (SPDC) can exhibit sharp correlations in the transverse spatial coordinates. This property leads to unique free-space propagation features. Here, we show that a phase object placed in the image plane of the source affects the free space propagation of the SPDC in a way that is mathematically analogous to the Fresnel diffraction of a first-order coherent source. This effect can be observed via the extraction of correlation images. We demonstrate this prediction with an experiment where the diffraction of correlated bi-photons is detected using an event-based camera. The results allow us to reconstruct the phase structure of the sample via non-interferometric phase retrieval methods. We verify that the retrieved phase patterns exhibit an enhanced contrast due to the probe two-photon nature. Our findings offer applications for non-interferometric, quantum-enhanced phase imaging.