Collective cavity Rayleigh scattering of an atomic array

Collective coupling between an optical cavity and multiple atoms facilitates enhanced light-matter interfacing, long-range interactions, and entanglement generation among all coupled atoms. Here we demonstrate such cooperative interactions through cavity Rayleigh scattering from an atom array. Each atom in the array has a thermal spreading much smaller than the cavity wavelength. We are able to move the position of atoms continuously, thus controlling the phase and amplitude of the atom-cavity interaction. For a pair of atoms, we observe constructive and destructive interference at spacings of integer and half-integer wavelengths, respectively. For an atom array with N atoms located at cavity antinodes of the same phase, we observe a near N² scaling of superradiant scattering rate, as well as spectral shifts and broadenings due to cavity backaction.