Quantitative phase gradient microscopy with spatially entangled photons

TL;DR

This paper introduces a quantum entanglement-based microscopy method that enables high-resolution, non-invasive phase and amplitude imaging without traditional interferometry or scanning, achieving record sensitivity with minimal light exposure.

Contribution

The authors develop a novel quantum ghost imaging technique that extracts full phase and amplitude information nonlocally, surpassing classical methods in resolution, sensitivity, and robustness against background noise.

Findings

Achieved 2.76 μm spatial resolution in phase imaging.

Demonstrated phase sensitivity of λ/100 with femtowatt illumination.

Provided robust imaging in complex lighting conditions.

Abstract

We present an entanglement-based quantitative phase gradient microscopy technique that employs principles from quantum ghost imaging and ghost diffraction. In this method, a transparent sample is illuminated by both photons of an entangled pair - one detected in the near-field (position) and the other in the far-field (momentum). Due to the strong correlations offered by position-momentum entanglement, both conjugate observables can be inferred nonlocally, effectively enabling simultaneous access to the sample's transmission and phase gradient information. This dual-domain measurement allows for the quantitative recovery of the full amplitude and phase profile of the sample. Unlike conventional classical and quantum phase imaging methods, our approach requires no interferometry, spatial scanning, microlens arrays, or iterative phase-retrieval algorithms, thereby circumventing many of their associated limitations. Furthermore, intrinsic temporal correlations between entangled photons provide robustness against dynamic and structured background light. We demonstrate quantitative phase and amplitude imaging with a spatial resolution of 2.76 $\mu$m and a phase sensitivity of $\lambda/100$ using femtowatts of illuminating power, representing the highest performance reported to date in quantum phase imaging. This technique opens new possibilities for non-invasive imaging of photosensitive samples, wavefront sensing in adaptive optics, and imaging under complex lighting environments.