  Recent advances in photonics have revived the interest in intensity
interferometry for astronomical applications. The success of amplitude
interferometry in the early 1970s, which is now mature and producing
spectacular astrophysical results (e.g. GRAVITY, MATISSE, CHARA, etc.), coupled
with the limited sensitivity of intensity interferometry stalled any progress
on this technique for the past 50 years. However, the precise control of the
optical path difference in amplitude interferometry is constraining for very
long baselines and at shorter wavelengths. Polarization measurements are also
challenging in amplitude interferometry due to instrumental effects. The
fortuitous presence of strong groups in astronomical interferometry and quantum
optics at Universite Cote d'Azur led to the development of a prototype
experiment at Calern Observatory, allowing the measure of the temporal
correlation g(2)(\tau, r=0) in 2016 and of the spatial correlation g^(2)(r) in
2017 with a gain in sensitivity (normalized in observing time and collecting
area) of a factor ~100 compared to Hanbury Brown and Twiss's original Narrabri
Interferometer. We present possible ways to further develop this technique and
point to possible implementations on existing facilities, such as CTA, the VLTI
ATs or the summit of Maunakea, which offer a unique scientific niche.
