Beitrag zur Untersuchung der estländischen Schieferöle : Inaugural-Dissertation zur Erlangung der philosophischen Doktorwürde

http://tartu.ester.ee/record=b2419396~S1*es

Effects of interatomic interaction on cooperative relaxation of two-level atoms

We study effects of direct interatomic interaction on cooperative processes in atom-photon dynamics. Using a model of two-level atoms with Ising-type interaction as an example, it is demonstrated that interparticle interaction combined with atom-field coupling can introduce additional interatomic correlations acting as a phase synchronizing factor. For the case of weakly interacting atoms with $J<\hbar\omega_0$, where $J$ is the interparticle coupling constant and $\omega_0$ is the atomic frequency, dynamical regimes of cooperative relaxation of atoms are analyzed in Born-Markov approximation both numerically and using the mean field approximation. We show that interparticle correlations induced by the direct interaction result in inhibition of incoherent spontaneous decay leading to the regime of collective pulse relaxation which differs from superradiance in nature. For superradiant transition, the synchronizing effect of interatomic interaction is found to manifest itself in enhancement of superradiance. When the interaction is strong and $J>\hbar\omega_0$, one-partice one-photon transitions are excluded and transition to the regime of multiphoton relaxation occurs. Using a simple model of two atoms in a high-Q single mode cavity we show that such transition is accompanied by Rabi oscillations involving many-atom multiphoton states. Dephasing effect of dipole-dipole interaction and solitonic mechanism of relaxation are discussed.Comment: 34 pages, 8 figure

Exchange broadening of EPR line in ZnO:Co

We study the X-band EPR spectra of Co²⁺ in single crystalline Zn₁₋xCoxO (x = 0.001–0.075) thin films grown by plasma-assisted molecular beam epitaxy. By analyzing the EPR linewidth behavior we argue that the exchange-narrowing model, usually applied to Mn-based II-VI DMS, fails here and that a combined effect of exchange and dipolar broadening can explain the linewidth variation with Co content and temperature

Quantum optical memory protocols in atomic ensembles

We review a series of quantum memory protocols designed to store the quantum information carried by light into atomic ensembles. In particular, we show how a simple semiclassical formalism allows to gain insight into various memory protocols and to highlight strong analogies between them. These analogies naturally lead to a classification of light storage protocols into two categories, namely photon echo and slow-light memories. We focus on the storage and retrieval dynamics as a key step to map the optical information into the atomic excitation. We finally review various criteria adapted for both continuous variables and photon-counting measurement techniques to certify the quantum nature of these memory protocols

Põlevkivist saadavatest immutusainetest

Digiteeritud Euroopa Regionaalarengu Fondi rahastusel, projekti "Eesti teadus- ja õppekirjandus" (2014-2020.12.03.21-0848) raames.https://www.ester.ee/record=b2263599*es