Two-photon-absorption measurements in the presence of single-photon losses

We discuss how two-photon absorption (TPA) of squeezed and coherent states light can be detected in measurements the transmitted fields. Such typically suffer from competing loss mechanisms such as experimental imperfections (i.e., imperfect photodetectors) other linear scattering losses inside sample itself, which lead to incorrect assessments two-photon-absorption cross section. evaluate sensitivity with TPA find that at sufficiently large photon numbers vacua or become independent occur after event has taken place. In particular, this happens for number antisqueezed field quadrature, where fluctuations counteract exactly cancel degradation caused by single-photon losses.