Photodetection, the Photon Echo, and Unitarity

Seng‐Tiong Ho

Leonid A. Vainshtein

Christopher J. Oliver

Tsuyoshi Fukuo, Tetsuo Ogawa, Katsuhiro Nakamura

We show that a system managed by quantum theory bears chaotic behavior induced by unitarity collapse in its time development. Nonunitary time evolution of the Jaynes-Cummings (JC) model, the interacting system consisting of two subsystems (a two-level atom and a quantized photon field), under a continuous quantum-nondemolition (QND) measurement of the photon number is investigated. In the regime of weak coupling between the subsystems, the measured system shows the Rabi oscillation and the decrease of the photon number variance, which mimic the unmeasured JC system and the photon field under the continuous QND photodetection, respectively. In the strong-coupling regime, the quantum system shows a nonintegrable nature, that is, it yields weak chaos characterized by both the broad continuous power spectrum and the decaying correlation function due to the lack of quantum recurrence.

David L. Falkoff, E. Lipworth

Theoretical studies have been made of the quantum mechanical description of coherence in materials such as ferromagnets and superconductors and of electromagnetic radiation. In the latter studies, application has been made to effects of coherence and high power on photodetection. A practical result is that the photon echo measurement is shown to provide a sensitive detector of coherence. Experimental work has been carried out to determine the diffusion coefficients and spin depolarization cross sections of optically pumped alkali vapors in noble buffer gases. A method has been developed to measure the density of cesium vapor as a function of temperature. (Author)

Michel De Haan