Entanglement Enabled Intensity Interferometry of different wavelengths of light

We propose methods to perform intensity interferometry of photons having two different wavelengths. Distinguishable particles typically cannot interfere with each other, but we overcome that obstacle by processing the via entanglement and projection so they lead same final state at detection apparatus. Specifically, discuss how quasi-phase-matched nonlinear crystals can be used convert a quantum superposition light wavelengths onto common wavelength, while preserving phase information essential for their meaningful interference. thereby gain access host new observables, which probe subtle frequency correlations entanglement. Further, generalize van Cittert–Zernike formula extended sources, demonstrate our proposal supports enhanced resolution sources spectral character, suggest potential applications.