Intensity interferometry with more than two detectors?

TL;DR

This paper explores the potential of multi-detector intensity interferometry, especially with three detectors, to enhance astronomical imaging and test quantum optics predictions, building on historical HBT experiments.

Contribution

It analyzes the feasibility and scientific benefits of extending intensity interferometry to three or more detectors, highlighting new measurement possibilities.

Findings

Three-detector HBT correlation could be measurable for bright stars.

Higher-order correlations increase combinatorially with the number of detectors.

Three-detector HBT can provide additional image information like the bispectrum.

Abstract

The original intensity interferometers were instruments built in the 1950s and 60s by Hanbury Brown and collaborators, achieving milli-arcsec resolutions in visible light without optical-quality mirrors. They exploited a then-novel physical effect, now known as HBT correlation after the experiments of Hanbury Brown and Twiss, and nowadays considered fundamental in quantum optics. Now a new generation of inten- sity interferometers is being designed, raising the possibility of measuring intensity correlations with three or more detectors. Quantum optics predicts some interesting features in higher-order HBT. One is that HBT correlation increases combinatorially with the number of detectors. Signal to noise considerations suggest, that many-detector HBT correlations would be mea- surable for bright masers, but very difficult for thermal sources. But the more modest three-detector HBT correlation seems measurable for bright stars, and would provide image information (namely the bispectrum) not present in standard HBT.