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Farrokh Vakili coauthored a modern stellar intensity interferometry experiment using two one-metre optical telescopes separated by fifteen metres. The team correlated photon-counting signals from bright stars, reviving a technique historically associated with Robert Hanbury Brown.

The measured quantity was the zero-delay correlation between detected light intensities. Its contrast contains information about angular source structure. The team measured reliable visibilities for two marginally resolved stars and found reduced contrast for a binary star, consistent with its more extended apparent structure.^[ref]

An experimental optical physicist who coauthored stellar stellar intensity interferometry measurements. Correlating fluctuations detected at separated telescopes probes the spatial coherence of starlight. The method extracts angular information from photon statistics rather than requiring the optical electric fields from the telescopes to remain phase locked.^[ref]

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]

An experimental optical physicist who coauthored stellar stellar intensity interferometry work, publishing under the surname Fouché. The experiment correlated fluctuations of starlight recorded by separate telescopes, applying the Hanbury Brown and Twiss effect to astronomical observations.^[ref][ref]

For one selected polarization of waves, write the detected complex fields as $E_1(t),E_2(t+\tau )$ and their light intensities as $I_j=|E_j{|}^2$, absorbing a common conversion constant. With stationary ensemble averages and nonzero ${\bar{I}}_j=⟨I_j⟩$, defineHere second-order optical coherence concerns distinct detector channels, with the corresponding normal ordering in the quantum formulation. Independent detection has $g^{(2)}=1$. Subtracting the means gives the normalized covarianceThus multiplying raw photocurrents contains a large mean-product contribution; multiplying their fluctuations isolates the small excess. Independent detector shot noise does not supply a mean cross-channel excess, although it increases measurement uncertainty.

The displayed Siegert relation requires a zero-mean, jointly circular complex Gaussian random field, the usual chaotic thermal light model. Circular means invariance under a common arbitrary complex phase rotation; in particular $⟨E_i{E}_j⟩=0$. Apply the Gaussian moment pairing theorem to the real and imaginary parts:The remaining pairing vanishes by circularity. Division proves the Siegert relation. Gaussianity is an assumption about fourth moments, not a consequence of merely measuring first-order optical coherence; a coherent state or photon antibunching cannot be interpreted by this thermal formula.

For equal-intensity beams combined in a common optical mode with matched wave polarizations, interferometric visibility is $V=|g_{12}^{(1)}|$. Consequently ideal thermal stellar intensity interferometry measures $g^{(2)}-1=V^2$, while the full $g^{(2)}$ includes the independent-count reference one. Unpolarized thermal light with two independent equally populated wave polarizations has half this excess: adding their covariances doubles the numerator while multiplying total means quadruples the denominator. Finite detector response further suppresses the peak and must be calibrated.^[ref]

An experimental optical physicist who coauthored measurements of the spatial coherence of three bright stars. Separate telescopes recorded intensity fluctuations whose correlations depend on their separation, applying stellar intensity interferometry to angular measurements. The approach links a laboratory quantum-optics correlation to a stellar observation.^[ref]