Generating quantum coherence with incoherent radiation

In multi-level quantum systems, coherent superposition states can unexpectedly arise from interactions with the continuum of modes associated with incoherent processes, such as spontaneous emission and incoherent pumping. This type of coherence, known as noiseinduced Fano coherence, represents a novel observation that has not yet been documented. In this thesis, I investigate a V-type three-level quantum system driven by incoherent radiation, examining both isotropic and unpolarized as well as anisotropic and polarized fields. The study identifies conditions for achieving quasi-stationary and stationary Fano coherence between the excited levels of the system within an overdamped dynamical regime. An optimization analysis of the main parameters, as the frequency splitting Δ between the excited levels, the intensity n of the incoherent radiation and the alignment parameter p between transition dipole moments, provides a suitable scenario for the detection of Fano coherence. The V-type system is then implemented in the hyperfine structure of hot 87Rb atoms inside a vapor cell and a proof-of-principle experiment is designed and conducted. The experimental setup employs angle-resolved fluorescence measurements to detect Fano coherence through spatial anisotropy in the emitted fluorescence around the vapor cell. Preliminary results are promising and are consistent with theoretical predictions. Additionally, the thesis explores the quantum thermodynamics of noise-induced Fano coherence to certify the presence of genuinely quantum traits underlying its generation. This includes analyzing the conditions under which the Kirkwood-Dirac quasiprobability distribution of the stochastic energy changes exhibits negativity, indicating non-classical traits. The study also demonstrates the existence of nonequilibrium regimes where, the generation of coherence leads to a significant excess of energy compared to the initial state, provided that the system begins in a superposition of energy eigenstates. Understanding how Fano coherence arises in multi-level systems through incoherent optical processes is crucial for its potential applications in enhancing the efficiency of quantum heat engines, photosynthetic light-harvesting complexes, and photovoltaics. The associated excess energy could be exploited as extractable work by external loads or storage systems, thereby offering significant technological advancements.