Theory of Non-Markovian dynamics in resonance fluorescence spectra

Abhishek Kumar

K. Wódkiewicz

Abhishek Kumar

Robust quantum coherence is an important prerequisite for any system that may be used to perform quantum information processing tasks. For systems that can be probed optically, the fluorescence spectrum may provide indirect evidence of coherence times when supplemented with an appropriate model of the decay process. A common approach is to assume a Markovian system, resulting in exponential decay of correlation functions and Lorentzian features in the associated spectrum. For physical systems with strongly history-dependent (non-Markovian) dynamics, there is currently limited systematic theoretical approach to establish the associated spectrum. In this thesis, we present a detailed theoretical method to obtain the fluorescence spectrum for a general system undergoing non-Markovian dynamics. This procedure can be used to systematically account for features in fluorescence spectra due to genuine non-Markovian dynamics. We apply this method to study the non-Markovian behaviour in the side peak of the Mollow-triplet and absorption spectrum of coherent population trapping systems.

R. I. Sokolovskiǐ

Sebastian Toivonen, Kimmo Luoma

We investigate a quantum dot (QD) system coupled to a vibrational environment with a super-Ohmic spectral density and weakly to a leaky cavity mode, a model relevant for semiconductor-based single-photon sources. The phonon coupling induces dephasing and broadens the absorption and emission line shapes, while the weakly coupled cavity mode leads to effective driving of the QD. To capture non-Markovian effects, we use non-Markovian Quantum State Diffusion and its hierarchical extension the Hierarchy of Pure States to compute multitime correlation functions underlying absorption and resonance fluorescence spectra. We present numerical results for the absorption spectra at strong phonon coupling and finite temperature, as well as for resonance fluorescence spectra at varying phonon coupling strengths and temperatures, and analyse the visibility of the resonance fluorescence spectra to provide insights into how phonon coupling and thermal effects influence the spectral features.

Felipe Caycedo‐Soler, Ferney J. Rodríguez, Luis Quiroga +2 more

The dissipative dynamics of a confined single exciton coupled to a reservoir is investigated beyond the Born‐Markov approximation. Specifically, the resonance fluorescence main features are studied as the coupling strength is varied with respect to the driving laser intensity. To the lowest order, the effective Hamiltonian is treated stochastically, from which an analytical solution of the fluorescence spectrum shows the basic features of a non‐Markovian noise induced dynamics. Finally, we discuss some aspects of higher‐order effects in the non‐Markovian system‐bath dynamics.