How quantum is the “quantum vampire” effect: testing with thermal light

The “quantum vampire” effect introduced in Optica 2, 112 (2015) is discussed to understand whether it is really quantum, i.e., based on entanglement and “nonlocality,” or whether photon number correlations are enough. For this purpose, the effect was demonstrated with the classical thermal state of light. We have shown, both theoretically and experimentally, that if a thermal state is distributed among several optical modes, and photon annihilation takes place in one of them, it leads to photon annihilation in the rest of the modes as well. Thus, we conclude, that quantum vampire is actually a classical effect, based on photon number correlations like ghost imaging, Hong-Ou-Mandel interference, and so on.