Quantum light driven many level systems in the weak and strong coupling limits

Abstract

We propose a possibility to study the quantum light excitation of atomic systems. To confine our study, we limit the configuration to two and four level emitters as target systems. Source and target are coupled via unidirectional waveguide. We numerically implement the cascaded formalism and use the source-target approach. Herein, we focus on continuous excitation scenarios where the source system is excited by continuous incoherent or coherent pumping. We demonstrate that, to a certain extent, one can control the target system's photon statistics via the source system pumping mechanism. Additionally, different coupling regimes in both cavities can change the output of the target system. In addition, we show that via tuning the cavity’s parameters one can produce an exotic type of quasi-probability distributions, a flat Fock state distributions. We also discuss the different obtained photon statistics for different coupling regimes. The used quantum light source, driven by spontaneous emission, can be categorized as a single photon source or two photon source. Therefore, the thesis is divided also according to these types of quantum light sources into two parts: In the first part of the thesis, after review of the theoretical methods, which are applied in the thesis , we specifically study coupled cavities. The first cavity, pumped incoherently, performs effectively as a single photon source. We consider system-bath interaction in the coupling waveguide, i.e boson-boson interaction, for the photon occurring in the system .We demonstrate that even for a simple scenario , where thermal bath modes couple to the system, the photon statistics of the source is not completely mapped to the target system. This suggest that the environment for such a coupled systems influence the photon statistics of the source while transferring it into the target system. In the case of direct coupling of emitters to the waveguide the influence of the environment, as a dissipator, on the photon statistics can be seen in photon number distribution. Additionally, higher order correlation functions for the target system deviate drastically from the source system and show a mixture of quantum coherent and incoherent dynamics. For the case of indirect coupling of emitters to the waveguide, when the modes of two cavities are coupled, the mediating environment also influences the photon statistics of the target system. This phenomenon manifests itself in the second-order correlation function of the source and target, wherein, while the source behaves in the anti-bunched regime, the target system shows highly bunched pattern. In the second part of thesis, we study the production of two photons in nonlinear optics. As an example, we propose an optical setup where we can produce entangled pairs of photons through the dynamical Casimir effect(DCE). By applying the laser on a superconducting surface of a metal dielectric we induce a surface plasmon polariton (SPP). SPP give rise to the enhancement of DCE such as the efficiency of two photon production exceed the common nonlinear optical processes for instance parametric down conversion. We show that the resonant enhancement of the emission of two photons happens when the excitation wavelength coincides with the amplitude of the laser light. Another even more efficient source for the two photon emission is a biexciton excitation of a quantum dot. We provide a formalism for a cascaded biexciton which can be used to show how the source biexciton, pumped coherently or incoherently, influences the target biexciton through a unidirectional waveguide, modeled as a thermal bath.