Quantum optics with giant atoms in imperfect waveguides

Sammanfattning

The rapid advancement of quantum technologies has driven the exploration of novelregimes in quantum light-matter interactions to overcome fundamental limits incoherence and control. Giant atoms, characterized by their ability to couple to awaveguide at multiple points separated by distances comparable to the wavelengthof the guided light, have emerged as a promising platform for quantum optics. Thephase shifts accumulated by photons traveling between these coupling points giverise to both self-interference and collective interference effects. Self-interference allowsa single giant atom to decouple from its environment, preventing relaxationinto the waveguide. For multiple giant atoms, the interference effects provide twomechanisms for decoherence suppression: the formation of dark states in driven andundriven systems and decoherence-free interaction (DFI) in a certain configuration.Previous studies in this emerging field have assumed the waveguide to be lossless.In this thesis, we investigate the impact of two realistic imperfections: losses in thewaveguide and asymmetric coupling, where the relaxation rates at each couplingpoint are unequal. Utilizing the SLH formalism for cascaded quantum systems, wederive the Lindblad master equation to model the dynamics of the system. Throughnumerical simulations, we quantify the extent to which these imperfections influencegiant-atom phenomena. Our results determine the upper bounds of losses perdistance in recent experiments and also the tolerances of losses in forming a highlyentangled state. The results presented in the report introduce essential, realisticconsiderations for topology designs and driven configurations in future giant-atomexperiments, laying the foundation for realizing implementations in quantum technologies.