Evolutionary Dynamics Of Ultra-cold Rydberg Atomic System

Rydberg is an atom with a large principal quantum number n and has many unique characteristics.It has broad application prospects in the fields of quantum information processing,quantum computing,precision measurement,and many-body physics.Rydberg atom has small energy spacing(?n-3),large transition matrix elements(?n2),which can generate millimeter waves or even centimeter waves.Superradiance is trigger when wavelengths of the emitted photon are larger than dimensions of the atom ensemble.The ultra-cold Rydberg atom ensemble is an ideal system for studying superradiance.Superradiance is a kind of coherent spontaneous radiation,which is an ensemble of excited atoms and molecules can synchronize emission of light collectively.Superradiance is paradigmatic of photon-matter interactions,and play fundamentally important roles in the study of nonlinear and quantum optics,and many-body physics.Superradiance moreover finds quantum technological applications in quantum metrology,superradiant laser,and atomic clocks.Here we report |nD5/2>?|(n+1)P3/2>evolutionary dynamics.We have observation of superradiance of |nD5/2>Rydberg states of cesium atoms enhanced by room-temperature BBR atoms in free space for the first time.It is the first time find that the strong long-range interaction(vdW)between Rydberg atoms plays an important role in the superradiance process.The vdW interaction will slow down the superradiation process,confirmed by large scale numerical simulations.Main contents are as follows:1.The Rydberg atom superradiance theoretical model and simulation are introduced,starting from the decay and lifetime of atoms,find that Black body radiation enhances the decay rate of Rydberg atoms and superradiance.Bulit a theoretical model of Discrete Truncated Wigner Approximation(DTWA),it is first time numerically simulated the effects of initial atomic population and vdW interaction on Rydberg superradiation.The vdW interaction will slow down the superradiation decay.2.We measures 60D5/2 Rydberg atoms lifetime,and analyzes the experimental results.The experimental results are similar to the effective lifetime when consider blackbody radiation at room temperature.And measure the nS1/2 and nD5/2 Rydberg atom lifetime,the dependence of the Rydberg atom lifetime on the principal quantum number n is obtained.3.We directly measure BBR enhance superradiant decay dynamics in selective |nD5/2>?(n+1)P3/2>transition of cesium Rydberg in free space.And investigating dynamics of Rydberg superradiance with respect to Rydberg atom number,principal quantum number n,vdW interactions.We first find that the van der Waals interactions between Rydberg atoms change the superradiant dynamics and modify the scaling of the superradiance.Obtain the dependence of the decay rate ?c and the maximum number of radiation photons Rmax on the initial atomic population.Theoretical simulations confirm the BBR enhanced superradiance in large Rydberg ensembles.4.The effect of the external field on the superradiance decay is introduced.The electric field can suppress the superradiance decay and microwave field can enhance the superradiance decay.Based on the Rydberg atom EIT-AT spectrum in the room temperature Cs vapor cell,investigate the nonlinear effect of the microwave electric field,by employing beat technique realize weak microwave measurement.The innovations of this work:1.Bulit Rydberg atom superradiation theoretical model,using DTWA(discrete truncated Wigner approximation)numerically simulate the superradiance of a polyatomic ensemble.It is the first time to theoretically study the long-range vdW interaction on the ultra-cold Rydberg|nD5/2>?|(n+1)P3/2>superradiance decay.2.Our work on the superradiant decay is for an ensemble of cold Rydberg atoms in free space,while the researches reported before largely focused on the superradiance of Rydberg atoms in cavities or beams of Rydberg atoms.We have identified the superradiant transition,measured population dynamics,and obtain the dependence of the decay rate ?c and the maximum number of radiation photons Rmax on the initial atomic population.The theoretical simulation is consistent with the experimental measurement results.3.We find for the first time that the van der Waals(vdW)interaction plays important roles during superradiance.We have shown experimentally that angular dependent dipole-dipole interactions are canceled out without external electric fields.However the vdW interaction can not be neglected,and it changes the time scale for the superradiant decay.