Deleterious effect of photon-phonon coupling on microcavities in their application as quantum sources

In quantum systems, the contact with the environment is detrimental to the purity of the state, thus limiting the practical use of entangled sources in quantum information applications. This loss of purity is observed in the form of additional noise in the tomography of the state. We investigate this noise dependence in Si 3N 4 micro-cavities, previously used for quantum state generation, and demonstrate that the dependence of this noise on the temperature is compatible with a coupling of the photonic chips to a thermal reservoir. The control of this noise source is a necessary condition for the efficient implementation of these devices as sources of entangled states in quantum networks.