Interaction with Photons

Quang Quy Ho

After researching carefully the well known M. Planck’s law of the black-body radiation, the quantum theory of field and the Einstein’s postulates about interaction of the photon with the atoms, there are a lot of unclear questions about photon and its interaction with atom. From all the above questions, there are three main following questions: Why does the energy of a light mode include zero-point energy? Where does the first photon come from in universe? and What is the first fact as a reason of absorption, emission in the photon-atom interaction? To find out the acceptable answers, here we propose postulates about the zero-photon and then about the new concepts of photon. Using them, we have tried to describe the basic characters of the photon and explain the photon-atom interaction in other way: the spin-spin interaction. Our results showed out the different picture of mechanism of the photon-atom interaction, the existence of the zero-photon energy, the absorption as well as the emission rule and its probabilities.

Aharon Brodutch, Eliahu Cohen

We present a scheme to generate an effective interaction Hamiltonian for systems that cannot interact directly and show how it can be used in scenarios such as non-local measurements and photon-photon interactions.

Chai Yeh

Julian W. Gardner

Enrico Stein, Axel Pelster

Abstract Although photon Bose–Einstein condensates have already been used for studying many interesting effects, the precise role of the photon–photon interaction is not fully clarified up to now. In view of this, it is advantageous that these systems allow measuring both the intensity of the light leaking out of the cavity and its spectrum at the same time. Therefore, the photon–photon interaction strength can be determined once via analysing the condensate broadening and once via examining the interaction-induced modifications of the cavity modes. As the former method depends crucially on the concrete shape of the trapping potential and the spatial resolution of the used camera, interferometric methods promise more precise measurements. To this end, the present paper works out the impact of the photon–photon interaction upon the cavity modes. A quantum mechanical description of the photon–photon interaction, including the thermal cloud, builds the theoretical backbone of the method. An exact diagonalisation approach introduced here exposes how the effective photon–photon interaction modifies both the spectrum and the width of the photon gas. A comparison with a variational approach based on the Gross–Pitaevskii equation quantifies the contribution of the thermal cloud in the respective applications.