We study the resonance fluorescence properties of an optically active spin 1/2 system, elucidating the effects of a magnetic field on the coherence of the scattered light. We derive a master equation model for this system that reproduces the results of a two level system (TLS) while also being applicable to a spin system with ground state coupling. This model is then solved analytically in the weak excitation regime. The inclusion of spin dynamics in our model alters the properties of the coherently scattered light at a fundamental level. For a TLS the coherence properties are known to be determined by the input laser. We show that spin scattered light inherits the coherence properties of the spin. This mapping allows us to measure spin dynamics and coherence time through direct measurement of the scattered fields. Furthermore, we show the ability to resolve sub-natural linewidth zeeman splittings. Along with representing an invaluable tool for spin spectroscopy understanding the coherence properties of the spin-scattered field will be vital for spin-photon based quantum technologies.
We study the resonance fluorescence properties of an optically active spin 1/2 system, elucidating the effects of a magnetic field on the coherence of the scattered light. We derive a master equation model for this system that reproduces the results of a two level system (TLS) while also being applicable to a spin system with ground state coupling. This model is then solved analytically in the weak excitation regime. The inclusion of spin dynamics in our model alters the properties of the coherently scattered light at a fundamental level. For a TLS the coherence properties are known to be determined by the input laser. We show that spin scattered light inherits the coherence properties of the spin. This mapping allows us to measure spin dynamics and coherence time through direct measurement of the scattered fields. Furthermore, we show the ability to resolve sub-natural linewidth zeeman splittings. Along with representing an invaluable tool for spin spectroscopy understanding the coherence properties of the spin-scattered field will be vital for spin-photon based quantum technologies.
Resonance fluorescence of a two-level emitter displays persistently anti-bunching irrespective of the excitation intensity, but inherits the driving laser’s linewidth under weak monochromatic excitation. These properties are commonly explained in terms of two disjoined pictures, i.e., the emitter’s single photon saturation or passively scattering light. Here, we propose a unified model that treats all fluorescence photons as spontaneous emission, one at a time, and can explain simultaneously both the spectral and correlation properties of the emission. We theoretically derive the excitation power dependencies, measurable at the single-photon incidence level, of the first-order coherence of the whole resonance fluorescence and super-bunching of the spectrally filtered, followed by experimental confirmation on a semiconductor quantum dot micro-pillar device. Furthermore, our model explains peculiar coincidence bunching observed in phase-dependent two-photon interference experiments. Our work provides an intuitive understanding of coherent light-matter interaction and may stimulate new applications. Standard descriptions of resonance fluorescence consider either absorption and re-emission in a single-photon picture or passive scattering. This study shows that resonance fluorescence can be described by a pure quantum state of the emitter and photon, revealing a coherent superposition that challenges the conventional view of spontaneous emission as an incoherent process.
We show how to calculate the first- and second-order statistics of the scattered fields for an arbitrary intensity coherent-state light field interacting with a two-level system in a waveguide geometry. Specifically, we calculate the resonance fluorescence from the qubit, using input-output formalism. We derive the transmission and reflection coefficients, and illustrate the bunching and antibunching of light that is scattered in the forward and backward directions, respectively. Our results agree with previous calculations on one- and two-photon scattering as well as those that are based on the master equation approach.
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
The wealth of quantum coherence effects depending on the orientation of external magnetic field, the polarization of coupling and probe lights, and the Rabi frequency of the coupling beam are studied in transition ${F}_{e}=2\ensuremath{\leftrightarrow}{F}_{g}=3$ of Cs D2 line. The split of electromagnetically induced transparency (EIT) resonances on two or three resonances determined by the different combination of the polarization of interaction lights and the direction of applied magnetic fields is obtained. The shifting and widening of the EIT resonances with the strength of the magnetic field (i.e., Zeeman splitting in the upper and lower levels) and Rabi frequency of the coupling beam increasing are also discussed. It may develop into the potential application for tunable multichannel optical information storage. On the other hand, an explanation of observed asymmetry of spectra by laser frequency offset from the optical resonance is given with theoretical calculation, which is in good agreement with the experimental results.
Resonance fluorescence arises from the coherent interaction of laser light with a two-level system and constitutes a quantum light source exhibiting single-photon emission and antibunching, making it a fundamental building block for future quantum networks. Our recent work [Nat. Commun.16, 6453 (2025)10.1038/s41467-025-61884-x] demonstrates that under continuous-wave excitation and in the absence of pure dephasing, the single-time joint state of resonance fluorescence and the two-level system can be described by a pure entangled state. Here, we analyze the cross-correlation and auto-correlation properties of the quantum optical field generated by the interference of resonance fluorescence with laser light at the resonance excitation frequency. Simulation results indicate that by varying the intensity or phase of the interfering laser light, the higher-order coherence of the post-interference quantum optical field transitions from anti-bunching to super-bunching behavior, consistent with recent theoretical and experimental advances by mean-field engineering. This approach offers a complementary framework to characterize and manipulate the multiphoton quantum optical fields.