Non-stationary processes in a cavity

A.M. Fedotov, Nikolay B. Narozhny, Yu.E. Lozovik

L. A. Pokrovskii

Fedotov, A M, Narozhny, B N, Lozovik, Yu E

We consider an atom interacting with a quantized electromagnetic field inside a cavity with variable parameters. The atom in the ground state located in the initially empty cavity can be excited by variation of cavity parameters. We have discovered two mechanisms of atomic excitation. The first arises due to the interaction of the atom with the non-stationary electromagnetic field created by modulation of cavity parameters. If the characteristic time of variation of cavity parameters is of the order of the atomic transition time, the processes of photon creation and atomic excitation are going on simultaneously and hence excitation of the atom cannot be reduced to trivial absorption of the photons produced by the dynamical Casimir effect. The second mechanism is "shaking" of the atom due to fast modulation of its ground state Lamb shift which takes place as a result of fast variation of cavity arameters. The last mechanism has no connection with the vacuum dynamical Casimir effect. Moreover, it opens a new channel of photon creation in the non-stationary cavity. Nevertheless, the process of photon creation is altered by the presence of the atom in the cavity, even if one disregards the existence of the new channel. In particular, it removes the restriction for creation of only even number of photons and also changes the expectation value for the number of created photons. Our consideration is based on a simple model of a two-level atom interacting with a single mode of the cavity field. Qualitatively our results are valid for a real atom in a physical cavity.

M. Soltanolkotabi, M. H. Naderi

Xue Zhang, Tai-Yu Zheng, Tian Tian +1 more

The Dynamical Casimir effect and collective excitations in atom ensemble are investigated in a non-stationary cavity. The results show that the dynamical Casimir effect leads to the collective excitations of atom ensemble due to absorption of the created photons. This remarkable feature indicates that the atom ensemble can serve as a detector for the process of photon production in a non-stationary cavity. Therefore by measuring the collective excitations of the atom ensemble, the dynamical Casimir effect can indirectly be verified.

Ulrike Herzog

The model commonly used to describe non-Poissonian pumping of micrornasers refers to periodic pumping where the possible arrival times of the pump atoms are separated by constant time intervals.1 In contrast to this, we study a micromaser with strictly stationary pumping.2 We investigate the level-selective statistics of the atoms leaving the cavity as well as the photon statistics of the cavity field. Our method is based on treating the statistics of the arrival times of the individual pump atoms, which are in the upper state of the microwave transition, with the help of the theory of stochastic point processes.