Jean-Pierre Rivet coauthored measurements of stellar spatial coherence using intensity interferometry. Two separated optical telescopes recorded photon arrivals, and fast electronics measured the correlation of their intensity fluctuations.
Unlike combining optical field amplitudes directly, the experiment estimated a statistical correlation from many detected events. Observations of three bright targets tested how the contrast changed with angular source structure. The work demonstrated that modern photon-counting detectors could recover useful stellar visibilities with metre-class telescopes.[ref]
Spatial intensity interferometry on three bright stars by William Guerin and others. Author list and abstract: two-telescope arrangement, zero-delay correlation and target-dependent visibility
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