Abstract

Radiation from independently emitting quantum systems is considered. If the quantum systems are prepared by coherent excitation then the radiation exhibits interference fringes as the point of observation is changed. There are no interferences in the intensity pattern if the system is incoherently excited. However the study of intensity-intensity correlations shows interferences even if the system is incoherently excited i.e. even if the emitted photons are uncorrelated. This can be understood in terms of the interferences between multiple pathways for quantum transitions as well as the detection induced entanglement. The intensity-intensity correlations have non classical nature and obey the Bell’s inequalities. Such quantum interferences can be used for information processing and applications to quantum imaging.