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QUANTUM PROPERTIES OF FLUORESCENCE LIGHT EMITTED BY TWO LEVEL ATOMS INTERACTING VACUUM DRIVEN BY COHERENT LIGHT

GIRMA SHANBALI

Published Jun 29, 2026• 0 citations
Publisher

Abstract

Abstract This thesis presents an investigation into the quantum characteristics of fluorescence emitted by a two-level atom placed in the electromagnetic vacuum and driven by a classical coherent field. The theoretical analysis employs the Jaynes–Cummings model together with the master-equation formalism commonly used to describe open quantum systems. Within this framework, the work examines key nonclassical fea tures such as photon antibunching, sub-Poissonian statistics, and quantum regression. Particular emphasis is given to resonance fluorescence and the influence of weak and strong driving fields on the coherence properties of the emitted radiation. The master equation is solved in the long-time limit to obtain the evolution of relevant atomic expectation values, which are subsequently used to study population dynamics, mean photon behavior, and spectral features of the fluorescence signal. The study also highlights the role of vacuum fluctuations in spontaneous emission and their impact on the quantum behavior of the atom, ultimately providing insights into the generation of coherent and nonclassical light from driven atomic systems and their relevance to quantum communication and quantum information technologies. Keywords: Fluorescence, Jaynes–Cummings model, Photon statistics, Quantum optics, Two-level atom

DOI
10.20372/nadre:25415

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Abstract This thesis presents an investigation into the quantum characteristics of fluorescence emitted by a two-level atom placed in the electromagnetic vacuum and driven by a classical coherent field. The theoretical analysis employs the Jaynes–Cummings model together with the master-equation formalism commonly used to describe open quantum systems. Within this framework, the work examines key nonclassical fea tures such as photon antibunching, sub-Poissonian statistics, and quantum regression. Particular emphasis is given to resonance fluorescence and the influence of weak and strong driving fields on the coherence properties of the emitted radiation. The master equation is solved in the long-time limit to obtain the evolution of relevant atomic expectation values, which are subsequently used to study population dynamics, mean photon behavior, and spectral features of the fluorescence signal. The study also highlights the role of vacuum fluctuations in spontaneous emission and their impact on the quantum behavior of the atom, ultimately providing insights into the generation of coherent and nonclassical light from driven atomic systems and their relevance to quantum communication and quantum information technologies. Keywords: Fluorescence, Jaynes–Cummings model, Photon statistics, Quantum optics, Two-level atom
Abstract This thesis presents an investigation into the quantum characteristics of fluorescence emitted by a two-level atom placed in the electromagnetic vacuum and driven by a classical coherent field. The theoretical analysis employs the Jaynes–Cummings model together with the master-equation formalism commonly used to describe open quantum systems. Within this framework, the work examines key nonclassical fea tures such as photon antibunching, sub-Poissonian statistics, and quantum regression. Particular emphasis is given to resonance fluorescence and the influence of weak and strong driving fields on the coherence properties of the emitted radiation. The master equation is solved in the long-time limit to obtain the evolution of relevant atomic expectation values, which are subsequently used to study population dynamics, mean photon behavior, and spectral features of the fluorescence signal. The study also highlights the role of vacuum fluctuations in spontaneous emission and their impact on the quantum behavior of the atom, ultimately providing insights into the generation of coherent and nonclassical light from driven atomic systems and their relevance to quantum communication and quantum information technologies. Keywords: Fluorescence, Jaynes–Cummings model, Photon statistics, Quantum optics, Two-level atom
ABSTRACT T 0.1 Significance of the Study This study provides a comprehensive theoretical and numerical investigation of light emission from a two-level atom interacting with a squeezed vacuum field. By devel oping a model based on the squeezed Jaynes–Cummings Hamiltonian and formulating atomic evolution via the master equation, the work establishes a framework for un derstanding how quantum squeezing modifies atomic dynamics. Analysis of popula tion inversion and emission characteristics shows that squeezing can enhance or inhibit spontaneous emission, accelerate population oscillations, and induce spectral narrow ing, while the second-order correlation function g(2)(τ) reveals photon antibunching and nonclassical statistics. The study further examines two-atom systems coupled to a common squeezed vacuum, highlighting steady-state entanglement and nonclassical correlations in quadrature variances, emphasizing the role of squeezing as a quantum resource. Overall, these findings provide insight into the influence of squeezed reser voirs on spontaneous emission, coherence, photon correlations, and entanglement, with important implications for quantum optics, precision spectroscopy, quantum metrology, and quantum information processing. Keywords: Master equation; Power spectrum; Quantum entanglement;Spontaneous emission; Squeezed vacuum; Two-level atom
ABSTRACT T 0.1 Significance of the Study This study provides a comprehensive theoretical and numerical investigation of light emission from a two-level atom interacting with a squeezed vacuum field. By devel oping a model based on the squeezed Jaynes–Cummings Hamiltonian and formulating atomic evolution via the master equation, the work establishes a framework for un derstanding how quantum squeezing modifies atomic dynamics. Analysis of popula tion inversion and emission characteristics shows that squeezing can enhance or inhibit spontaneous emission, accelerate population oscillations, and induce spectral narrow ing, while the second-order correlation function g(2)(τ) reveals photon antibunching and nonclassical statistics. The study further examines two-atom systems coupled to a common squeezed vacuum, highlighting steady-state entanglement and nonclassical correlations in quadrature variances, emphasizing the role of squeezing as a quantum resource. Overall, these findings provide insight into the influence of squeezed reser voirs on spontaneous emission, coherence, photon correlations, and entanglement, with important implications for quantum optics, precision spectroscopy, quantum metrology, and quantum information processing. Keywords: Master equation; Power spectrum; Quantum entanglement;Spontaneous emission; Squeezed vacuum; Two-level atom
Analysis of the effects of decoherence on the radiative and squeezing properties of a coherently driven two-level atom trapped in a resonant cavity applying the corresponding master equation is presented. The atomic dynamics as well as the squeezing and statistical properties of the emitted radiation are investigated. It is found that the atom stays in the lower energy level more often at steady state irrespective of the strength of the coherent radiation and thermal fluctuations entering the cavity. Moreover, a strong external coherent radiation results in the splitting of the line of the emission spectrum, whereas the decoherence broadens the width and significantly decreases the height. It is also found that the emitted radiation exhibits photon anti-bunching, super-Poissonian photon statistics and squeezing, despite the presence of the decoherence which is expected to destroy the quantum features.
The collapse and revival of quantum states appear in diverse areas of physics. In quantum optics the occurrence of such a phenomena in the evolution of an atomic state, interacting with a light field initially in a coherent state, was predicted by using the Jaynes-Cummings model (JCM), and subsequently demonstrated experimentally. In this paper we revisit the JCM with the Monte-Carlo wave function approach and investigate the time evolution of the photon emission rate of the atom in a cavity. Analytical and numerical quantum trajectory calculations show that the cavity and the initial field statistics strongly influence the photon emission dynamics. A coherent field indeed gives rise to a collapse and revival behavior that mirrors atomic state evolution. However, there are differences between the two. The emission rate for a field in a Fock number state exhibits a sinusoidal oscillation, and there exists a quiescent period for a thermal field. These properties are quite different from those in free space. It is also shown that the fluctuation in photon emission is much less than that of the atomic population.
Quantum interference and coherence effects in the interaction of atoms with the quantized electromagnetic field are investigated theoretically. A general master equation for the description of atom-field interactions is introduced. The interplay of the concepts of complementarity and interference in the time-energy domain are studied on the basis of the fluorescence light emitted by a single laser-driven atom, where the coherence of spontaneous processes gives rise to quantum interference in the spectrum of resonance fluorescence. The vacuum-induced dipole-dipole interaction in pairs of multi-level atoms is analyzed. It is shown that the interaction between orthogonal transition dipole moments of different atoms does not only influence the system dynamics crucially, but implies that the few-level approximation in general cannot be applied to near-degenerate Zeeman sublevels of the atomic level scheme. Potential applications of dipole-dipole interacting multi-level atoms for the implementation of decoherence-free subspaces and the generation of entanglement between atomic states are examined. The generation of an entangled state of the radiation field with a macroscopic number of photons is discussed on the basis of a single-atom laser.