Towards Experimental Exploration Of Quantum Simulation In Ultracold Strontium Rydberg Gas

Ultracold gases of Rydberg atoms are extensively investigated in the fields of quantum computing,quantum simulation,and quantum sensing.While most studies focus on alkali species with one single valence electron,the two-valence-electron system like alkali-earth atoms attracts more and more attentions in the community providing the richer electronic structures and many potential applications of them.Here in this thesis,we will present both experimental and theoretical efforts in this direction.The ultimate goal of this study is to quantum simulate interacting spin models using a Rydbergdressed ultracold gas of ground-state strontium atoms.We first describe some details of an apparatus routinely producing ultracold gases of strontium atoms,including a dual-wavelength imaging system for systematically comparing a narrow-line absorption to a broad-line one.Strontium Rydberg states are addressed starting from the ground state via a two-photon process,where the intermediate level is meta-stable.Through measuring the Autler-Townes splitting of the 5sns 3S1 Rydberg series induced by a UV light coupling to the intermediate state,we have accurately mapped out the corresponding transition matrix elements,which agree quite well to theoretical calculations based on a single-active-electron model.We then present an experimental investigation of Rydberg-Rydberg interactions of the 5sns 3S1 series by monitoring trap-loss dynamics of the number of ground state strontium atoms with a multi-pulse two-photon excitation scheme to enhance the detection sensitivity.We model the observed dynamics using a mean-field description,where the Rydberg-Rydberg interaction is considered as a mean-field shift in a singleparticle optical Bloch equation.Coefficients of the van der Waals interaction are extracted through this modeling and then compared to theoretical calculations for five different principal quantum numbers which is agree well with the theoretical calculations.In the last part of this thesis,we investigate relaxation dynamics of a disordered Ising spin system,where a soft-core Ising interaction is considered.Such an interaction type can be realized via the so-called Rydberg dressing,which is our next experimental step.Concerning the relaxation of magnetization in this case,we have derived an analytic expression for a uniformly distributed spin system while numerical studies are performed for a Gaussian distributed one.In the former case,three different behaviors are observed in the dynamics and particularly a stretched-exponential decay is recovered at the long-time limit connecting to the recovery of scale invariance there.For the Gaussian case,the degree of disorder can be tuned by the spatial extension of the spin sample,which enables the study of quantum dynamics from a coherent evolution at the fully ordered limit to a disorder-dominated situation.In this part we also briefly introduce our experimental efforts in realizing a spin Hamiltonian by considering the two-level system of the ground and intermediate states.