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CNAA / Theses / 2022 / June /

Quantum dynamics in molecular dipolar systems


Author: Mîrzac Alexandra
Degree:doctor of physics and mathematics
Speciality: 01.04.02 - Theoretical and mathematical physics
Year:2022
Scientific adviser: Mihail Macovei
doctor habilitat, associate professor (docent)
Institution: Institute of Applied Physics of the

Status

The thesis was presented on the 17 June, 2022
Approved by NCAA on the 25 November, 2022

Abstract

Adobe PDF document – 1.53 Mb / in romanian
Adobe PDF document – 1.53 Mb / in english

Thesis

CZU

Adobe PDF document 2.25 Mb / in romanian
156 pages

Keywords

two-level system, three-level Λ-system, permanent dipole moment, resonance, fluorescence, squeezing, terahertz lasing, multi-quanta processes, quantum interference, multiphoton conversion, quantum emitter, super-Poissonian statistics

Summary

The thesis has been written in English language and consists of the introduction, 4 chapters, general conclusions and recommendations, and the list of 205 references. The thesis contains 134 pages of basic text, 19 figures and 141 formulae. The results presented in the thesis are published in 16 scientific papers.

The goal: The detection of new quantum dynamical properties in two and three-level Λ-type systems possessing a non-zero permanent dipole moment strongly coupled with quantum optical cavity or opto-mechanical resonators.

Research objectives: The calculation of squeezing effects in the resonance fluorescence processes of laser-pumped two-level system possessing a permanent dipole moment; The determination of the total quantum fluctuation spectra of laser-pumped dipolar two-level systems; The investigation of a laser-pumped three-level Λ-type system having the upper state coupled with a quantum oscillator described by a single quantized leaking mode; The identification of three-level model particularities leading to lasing and cooling effects; The demonstration of quantum interference effects induced by emitter’s dressed states responsible for flexible lasing and deeper cooling effects; The investigation of frequency conversion from optical to microwave region, via the resonant pumping of an asymmetrical two-level system incorporated in a quantized single-mode resonator; The demonstration of multiphoton features of cavity quantum dynamics containing an asymmetric two-level system using certain multiphoton superposition of generated states. Scientific novelty and originality of the results: the new features of resonance fluorescence spectrum of spontaneously emitted photons by dipolar two-level system were demonstrated; two distinct mechanisms of lasing and cooling based on single- or two-quanta processes where detected in the three-level Λ-type system; conversion of photons from optical to microwave domains, via resonantly pumped asymmetrical two-level quantum emitter embedded in a quantized single-mode resonator.

The main scientific problem solved consists in computing and analyzing the quantum dynamical properties of few level atomic systems possessing a permanent dipole moment interacting with external coherent laser field.

Theoretical significance and applicative value: in the thesis, one has investigated the steady state-quantum dynamics of a laser pumped two-level system possessing a non-zero permanent dipole moment. New features of the dipolar two-level system have been found in the resonance fluorescence spectrum, squeezing spectrum and total quantum fluctuations.

The model of a laser-pumped three-level Λ-type system with highest energetic level coupled with a quantum oscillator described by a single quantized leaking mode has been investigated. Two distinct regimes leading to cooling and lasing effects of the model have been identified. In the first regime, the model functions as a two-level system. Whereas in the second regime, the model evolves into a three-level equidistant system.
The quantum multiphoton dynamics of a two-level system possessing unequal permanent dipoles, placed in a leaking single-mode quantized cavity field and coupled to it has been investigated. The photons conversion from optical to microwave frequency domains was proved.

The implementation of the scientific results: the research presented in this thesis have been successfully implemented in the framework of the national project (15.817.02.09F) also with support of Moldavian National Agency for Research and Development, grant No. 20.80009.5007.07 and National Scholarship of World Federation of Scientists in Moldova.