  A theory of the IR-field-induced single-photon generation by the narrow
thin-film superconducting rings made of the isotropic s-wave pairing type-II
superconductors is presented. It is shown that statistical measurements of the
energies of photons emitted by the same current-carrying ring prepared
initially in the same quantum state, allow to find the number distribution of
Cooper pairs in the superconductor.
