Subdiffraction incoherent optical imaging via spatial-mode demultiplexing

TL;DR

This paper introduces a SPADE measurement scheme that significantly improves the resolution of incoherent optical imaging beyond the diffraction limit, approaching quantum-limited precision for estimating object parameters.

Contribution

The paper presents a practical SPADE measurement method that outperforms direct imaging in subdiffraction regimes and approaches quantum-optimal precision for parameter estimation.

Findings

SPADE can estimate moments of subdiffraction objects more precisely than direct imaging.

SPADE approaches the quantum limit in estimating object location and scale.

The scheme is feasible with current linear optics and photon counting technologies.

Abstract

I propose a spatial-mode demultiplexing (SPADE) measurement scheme for the far-field imaging of spatially incoherent optical sources. For any object too small to be resolved by direct imaging under the diffraction limit, I show that SPADE can estimate its second or higher moments much more precisely than direct imaging can fundamentally do in the presence of photon shot noise. I also prove that SPADE can approach the optimal precision allowed by quantum mechanics in estimating the location and scale parameters of a subdiffraction object. Realizable with far-field linear optics and photon counting, SPADE is expected to find applications in both fluorescence microscopy and astronomy.