Feedback-induced diverging two-photon correlation length in waveguide QED
Scattering of light strongly confined in low-dimensional waveguides has attracted considerable interest in recent years. Especially strong photon-photon interaction are generated by inelastic scattering on atomic structures enabling efficient control in the few-photon regime. We present a paradigmatic model exhibiting decaying quantum oscillations. Using time-delayed quantum coherent feedback control, we show that photons can be correlated over extreme long time-scales. Our effects demonstrates that two-photon quantum states can be stabilized via quantum feedback and reveal a strong non-Markovian behaviour.