Studys Of Novel Quantum Phenomena In Few-body Rydberg Systems

Based on the long radiation life,large dipole moment and long-range interaction,the Rydberg atoms play an important role in many quantum information and quantum computation tasks.Of particular concern is the strong dipole interaction between the Rydberg atoms leading to the so-called dipole blockade phenomenon: if two atoms are simultaneously excited to the Rydberg states by resonant driving laser fields,the Rydberg-state energy level will be shifted by the strong dipole interaction,causing the detuning between the atomic transition frequency and the driving laser frequency.Therefore,if one atom has been excited to Rydberg state,the same Rydberg state excitation of the neighboring atoms will be strictly suppressed to form the excitation blockade effect.Based on this dipole blockade effect,Rydberg atoms has been provided to be an effective platform for various quantum science tasks such as the preparation of quantum entanglement states,the preparation of reliable single photon source,the quantum platform for the simulation of condensed matter physics,and so on.In this paper,by adjusting the intensity of atomic interaction,and the atom-driven laser detuning,we study the manipulation of various quantum correlations between Rydberg atoms.We also explore the in-phase and anti-phase dynamics of two Rydberg atoms with distinguishable resonances,and the discrete time crystal features of a finite chain of Rydberg atoms is further discussed.In the third chapter,We study the steady-state quantum correlations arising from the atom–field and interatomic interplays in two-level Rydberg atoms coherently driven by an external laser field.Three kinds of quantum correlations,i.e.,atom–atom correlation,atom–field entanglement and photon–photon correlation,are simultaneously examined by considering dipole–dipole interactions(DDI)for pairwise Rydberg atoms.They are shown to be closely linked with single and double Rydberg excitations,which can be modulated to work in the blockade or antiblockade regime depending on the driving field frequency,the DDI strength and the Rydberg decay rate.As a result,we obtain strongly correlated atoms and highly antibunching photons(indispensable resources in applications of quantum information processing)intermediated with robust atom–field entanglement.In the fourth chapter,We study the correlated evolutions of two Rydberg atoms,interacting via a van der Waals(vdW)potential V6 and driven by a laser field of detunings.The two atoms may exhibit the inphase dynamics with identical Rydberg populations or the antiphase dynamics with complementary Rydberg populations,depending on their initial states.For a moderate vdW potential far from the blockade regime,the in-phase or antiphase dynamics can be attained along two intersecting lines in the parameter space of detuning with an exact or approximate figure of merit,respectively.Note,in particular,that the exact in-phase dynamics is trivial because it requires identical detunings while the approximate in-phase,exact antiphase,and approximate antiphase dynamics are nontrivial because they require distinct detunings.The specific requirements on detuning for both in-phase and antiphase dynamics can be understood by considering the balanced transitions from two initially populated states to two initially empty states in the double-atom state basis.In the fifth chapter,we investigate the collective behaviors of a finite chain of Rydberg atoms interacting via nearest-neighboring van der Waals potentials and driven by one laser field in a Floquet way.Our numerical results on Rydberg population evolution and its Fourier spectrum show that this Rydberg chain can display typical features of discrete time crystal(DTC),i.e.,spontaneous time-translation-symmetry breaking,strong robustness against perturbation,and the rapid growth of persistence versus the increase of system scale.Moreover,we find show that the stability of DTC can be greatly enhanced by moderate detuning.This result provide a effect scheme to prepare DTC in wider parametric range.We also study the boundary between the DTC phase and the chaotic phase.The results show that our model exhibit the stepped boundary effect against the increasing of the system scale.In summary,we expect that our work of the quantum correlations in Rydberg atomic system will not only benefit the research of Rydberg atoms in quantum information tasks,but also be a good foundation for the study of many-body quantum correlation and for the exploration in the relation between different quantum correlations.Our work of the In-phase and antiphase dynamics of Rydberg atoms with distinguishable resonances can help people to gain deeper insight about the coherent dynamical behavior of interacted Rydberg atoms,and these results should be instructive in devising schemes of quantum manipulation on atomic entanglement,though they are not easily extended for more Rydberg atoms in the 1D chains or 2D arrays.We also expect our results of the discrete time crystal with a finite chain of Rydberg atoms can not only be beneficial for the realization of discrete time crystals with Rydberg atom,but also be helpful for people to better understand the mechanism of time crystals.