Quantum coherence in the Dynamical Casimir Effect
  We propose to use quantum coherence as ultimate proof of quantum nature in the radiation that appears by means of the Dynamical Casimir Effect in experiments with superconducting microwave waveguides. We show that, unlike previously considered measurements of quantum correlations such as entanglement and discord, quantum coherence does not require a threshold value of the external pump amplitude and is highly robust to thermal noise. 
D. N. Samos-S\'aenz de Buruaga, Carlos Sab\'in
quant-ph