Research On Single-photon Transition Rydberg Excitation Of Cesium Atomic Ensemble With A 319-nm Ultraviolet Laser

The strong long-range dipole-dipole interactions between Rydberg atoms due to their large electric dipole moment can lead to Rydberg blockade.It is very promising for applications in many-body physics,quantum computing,quantum information,nonlinear optics and imaging.Moreover,Rydberg atom has huge electric polarizability,which makes it very sensitive to the external electric field.Besides,the electric field sensors based on Rydberg atoms need not be calibrated,which is important for application in the field of quantum metrology and precision measurement.Due to the low transition probability from ground state to Rydberg state and transition wavelengths in the range of violet or ultraviolet?UV?lasers,it is not easy to implement,so that the cascade two-or three-photon excitation is used to prepare highly-excited Rydberg atoms.However,compared with the multi-photon excitation scheme,the single-photon excitation can avoid atomic decoherence from population in the intermediate state,the photon scattering,and AC-Stark shift.Therefore,the single-photon excitation scheme has obvious advantages for the preparation of Rydberg-dressed ground-state atoms for quantum computing and quantum information.In this paper,we perform the single-photon Rydberg excitation of cesium atoms by using a self-developed high-power,narrow-linewidth,and tunable single-frequency 319 nm UV laser system.In the hot and cold ensembles of cesium atoms,the single-photon Rydberg excitation signal is observed by all-optical detection method,and Rydberg physics are studied.The main contents are as follows:?1?We study the generation process of high-power,narrow-linewidth and continuous tunable 319 nm UV single-frequency laser.A 319 nm UV laser with the 2-W output power is obtained by a second-harmonic generation via a four-mirror ring cavity following a single-pass sum-frequency generation of two narrow-linewidth lasers at 1560.5 nm and 1076.9 nm.We construct an ultra-stable optical cavity placed in ultra-high vacuum system,which is controlled by a high-precision temperature driver.Moreover,we stabilize a 319 nm UV laser to the ULE cavity by using the electronic sideband locking method.When the whole system keeps locked,the continuous tuning range of the UV laser is greater than 4 GHz,and frequency stability is less than 20 kHz.?2?Based on the self-developed 319 nm UV laser system,we perform the single-photon Rydberg excitation of 6S_1/2???nP_3/2?n = 70-100?in the room-temperature cesium vapor cell by using the all-optical detection method.We theoretically and experimentally study Autler-Townes splitting of Rydberg velocity-selective spectra in the strong coupling field and the dependence of Rydberg spectrum on the external magnetic field in detail.?3?We construct a magneto-optical trap system of cesium cold atom,and measure the relevant parameters.Then we perform the single-photon Rydberg excitation in the cold atomic ensemble by using trap-loss spectroscopy.The Autler-Townes splitting spectrum in the cold atomic ensemble is experimentally observed.Based on the huge electric polarizability of Rydberg atoms,we measure the background DC electric field by the Stark spectrum induced by the electric field.?4?We calculate the dynamic electric polarizability of cesium 6S1/2 ground state and n S1/2,n P3/2 Rydberg states,and determine the magic conditions of optical-dipole trap for confining the ground-state and Rydbergstate atoms.The optimal magic condition is found,and the relevant dissipation mechanisms affecting Rydberg lifetime in the trap are analyzed in detail.An 1879.43 nm magic optical-dipole trap is constructed to confine the 6S1/2 ground state and 84P3/2 Rydberg state of cesium atoms,and the polarization fluctuation and intensity noise of the 1879.43 nm laser are effectively suppressed.The innovation of this work:?1?The single-photon Rydberg excitation signal is detected by means of nondestructive all-optical detection.Compared with the traditional ionization detection method,the detected atoms can be repeatedly used,which is important for applications in the field of quantum information.?2?Compared with the multi-photon excitation scheme,singlephoton Rydberg excitation can weaken atomic decoherence from the population in the intermediate state,as well as the photon scattering and AC-Stark shift.In addition,compared with the single-photon Rydberg excitation with low-power pulsed light,we can achieve the coherent control of quantum state and study the related properties of cesium n P Rydberg states with the self-developed high-power narrow-linewidth continuous UV laser.?3?A magic optical-dipole trap for cesium Rydberg state is theoretically calculated and experimentally constructed.The optical dipole trap can not only confine both the ground state and Rydberg state of cesium atoms,but also have the same trap depth for the two states.Therefore,the magic trap can preserve the quantum coherence of ground-Rydberg states,and improve the repetition rate of the experimental sequence.It is of great significance for high-fidelity entanglement and quantum logic gate operation.