Dynamical echo in two-state quantum systems

M. Kira, S. W. Koch

R. Sankaranarayanan, Jane H. Sheeba, M. Lakshmanan

Evolution of quantum fidelity for two-level systems is studied in the context of periodic echo. From a general treatment for time independent case, we obtain a simple condition on the governing Hamiltonians under which the systems display periodic quantum echo. For a specific time dependent problem the quantum fidelity is shown to exhibit Rabi oscillation. This may be considered as a simple mechanism to generate periodic echo, except for a specific initial superpositional state in which case the fidelity remains invariant.

Li Yongfang

Using the method of the Bloch vectors,the physics mechanism of the photon echo is analyzed with both the dressed state and quantum interference theory,and the physics picture for the interaction between light and atoms is given in detail.The dynamic process for the quantum information storage and that of the recall with the photon echo is discussed under adiabatic condition.The results show that the photon information is stored in the medium during the first pulse,and when v and w of the Bloch vectors are inversed during the second pulse,the information reappears as the photon echo.The process of the photon echo is virtually the process of photon information storage and recall.

Gaetano Busiello, R. V. Saburova, F. S. Vagapova

Stephan Glutsch, U. Siegner, D. S. Chemla

We study the dynamics of coherent emission of a semiconductor within the framework of the semiconductor Bloch equations, both in the time domain and in real space for various excitation conditions. We find that the spatial properties of the four-wave-mixing (FWM) response reflect the well-known temporal dynamics. For excitation high above the band edge, the FWM signal is emitted as a photon echo. This photon echo from continuum states of a semiconductor has the same dynamical properties as a photon echo from inhomogeneously broadened uncoupled two-level systems. However, unlike the case of two-level atoms, the polarization of the photon echo from the semiconductor continuum extends over macroscopic distances in real space. The implications of the large spatial extent of the photon echo polarization are discussed. In particular, we show that, in spite of the macroscopic size of the photon echo polarization, the wavelength of the exciting light can still be neglected.

Hendra I. Nurdin, Naoki Yamamoto