Two-photon interference : new light on quantum nature

Enrique J. Galvez, M. Beck

We present new results of interference experiments for undergraduates that underscore the quantum nature of the light. The experiments use parametric down-conversion to generate pairs of correlated photons. The experiments involve one- and two-photon interference schemes that rely on first and second-order coherence effects. They can be used as a complement to teaching quantum mechanics or quantum optics.

Rainer Kaltenbaek, B. Blauensteiner, Markus Aspelmeyer +2 more

Z. Y. Ou

Manutea Candé, S. E. Skipetrov

We discuss quantum and classical aspects of two-photon interference in light transmission through disordered media. We show that disorder is the main factor that suppresses the interference, whatever the quantum state of the incident light. Secondarily, the two-photon interference is affected by the quantum nature of light (i.e., the well-defined number of photons in the two-photon entangled and Fock states as compared to the coherent state). And finally, entanglement is a resource that allows one to prepare two-photon states with special symmetries with respect to the interchange of the photons and, in particular, the states with bosonic and fermionic symmetries. The two-photon interference is more robust for the latter states and its sign can be inverted for the fermionic state.

Hongmin Liu

We report an experiment of observation of classical double-slit interference fringes of two-photon interference. In the experiment, a commercial continuous-wave multi-mode F-P laser diode without either mode-locked or frequency-locked is used as the light source, the density of photons is far more than the single-photon level, and the path difference of the long and short paths is far more than the longitudinal coherence length of the laser diode. The temporal stable and clearly visible spatial-distributed pattern, i.e. first-order interference fringes, was observed .Contradict to the prediction of single-photon interference mechanism, the interference happened far beyond the coherence length, the occurrence possibility and time duration of the interference fringes decrease with the reduction of mode number of the LD, and the time difference between the fringes disappearance and the light vanish is equal to the time difference of the two paths. After discussion, we came to the conclusion that the observed phenomena can be understood in time-resolved two-photon interference mechanism. We reveal a new method to perform two-photon first-order interference, and this help to understand the nature of two-photon interference and also can be useful for quantum information science.

David S. Simon, Gregg S. Jaeger, Alexander V. Sergienko