StatusThe thesis was presented on the 18 September, 2020 at the meeting of the Scientific Council and now it is under consideration of the National Council.
Abstract– 1.11 Mb / in romanian
– 1.11 Mb / in english
6.15 Mb /
The thesis has been written in English language and consists of the introduction, 5 chapters, general conclusions and recommendations, and the list of 200 references. The thesis contains 127 pages of basic text, 25 figures and 145 formulas. The results presented in the thesis are published in 20 scientific publications.
The goal: The determination and analysis of different quantum properties of the dynamics of an optical or mechanical resonator interacting with semiconductor artificial atoms.
Research objectives: The identification of various emitter-resonator coupling schemes related to different characteristic features of artificial atoms; The demonstration of the quantum statistics of an optical or mechanical resonator when interacting with an artificial atom; The identification of possible quantum interferences in systems possessing multi-level artificial atoms; The observation of the behaviour of the quanta distribution of a nanomechanical resonator under different interaction conditions; The demonstration of the influence of collective phenomena to the behaviour of an optomechanical system.
Scientific novelty and originality of the results: the phonon superradiant behaviour has been demonstrated in solid matter quantum nanomechanical resonators; the phenomenon of destructive quantum interference has been manipulated in order to effectively decouple an artificial atom from an optical cavity; a perturbation treatment of moderately strong quantum-dot-acoustic-resonator dynamics has allowed the observation of sub-Poissonian distributed phonon fields, i.e., quantum phonon lasing. The main scientific problem solved consists in analysing the phenomena related to the quantum statistics of different types of quantum oscillators interacting with artificial atoms, in order to predict the conditions required to prepare the quantum oscillator in a specific quantum state.
Theoretical significance and applicative value: in this thesis it was demonstrated the quantum dynamics of open quantum systems with an elevated degree of complexity, which include diverse interactions among various components such as artificial atoms, laser light, optical cavities, nanomechanical resonators and the surrounding environment.
The model of a pumped two-level quantum-dot coupled to a quantum mechanical resonator operating in a moderately strong coupling regime has been solved. A coherent phonon generation scheme with sub-Poissonian quantum distribution of the vibrational quanta of the acoustic nanomechanical resonator has been proposed in order to improve phonon based sensing techniques.
A setup made of an equidistant ladder-type three-level quantum-well with perpendicular dipoles placed in an optical cavity has been investigated in the good cavity limit. A scheme for a quantum switch based on quantum interference effect was proposed. The cavity electromagnetic field is turned on and off by varying the parameters of the input pumping lasers.
The collective behaviour of a sample of initially excited two-level quantum-dots placed on a quantum mechanical resonator has been reported among the firsts investigations in the current literature. Therefore, a mechanism generating phonons with fast dynamics has been established.
Ultra-short intense phonon pulses are generated via this mechanism, similarly to the superradiance effect.
The implementation of the scientific results: the research presented in this thesis has been successfully implemented in the framework of the bilateral moldo-german project 13.820.05.07/GF and national institutional project 15.817.02.09F, and may be further used for educational purposes.