Investigation On The Quantum Interference And Chiral Edge States With Cesium Atomic Systems

Atom-light coupling system is an important topic in the field of quantum optics,and plays a crucial role in the development of various quantum techniques,such as quantum communication,quantum computation,quantum precise metrology,etc.With the discovery of laser,the atomic coherence induced by laser field attracted enormous interests.The atomic coherence can lead to the quantum interference between different atomic levels,and thus electromagnetically induced transparency(EIT),which manifests as the dramatical suppression of absorption and the steep dispersion near atomic resonant frequency.Due to these remarkable features,EIT media has important applications in the fields of quantum memory,quantum simulation,all-optical devices.Recently,owing to the flexibly controllable optical properties,EIT media have been used to simulate many condensed physics phenomena,such as topological transition,edge current,etc.In particular,the conception of superradiance lattice in EIT systems paves the way to study quantum manybody physics in hot atoms.In this thesis,we firstly introduce and review several typical phenomena induced by atomic coherence in atom-light coupling system,such as EIT,photonic crystals,superradiance lattice,etc.Then,we investigate the influences of dephasing on quantum interference in various three-level atomic systems,and present the relevant experiment verification.Finally,we present the observation of chiral edge current in superradiance lattice created by EIT with hot cesium atomic vapor.The main contents are as follows:1)We investigate the influences of coupling-field intensity and dephasing rates on the relative weights of quantum interference and Autler-Townes splitting(ATS)in Λ-type EIT system.The transparency window in an EIT spectrum is a joint effect of quantum interference and ATS,but it is difficult to intuitively distinguish the two effects.Since the quantum interference can dramatically change the properties of media,it has important applications in development of quantum techniques.Also,the wide transparency window in ATS has been used in high-resolution spectroscope and high-speed broadband storage of photons.Therefore,distinguishing of quantum interference and ATS is of vital significance.In an EIT system,the coupling-field intensity and the dephasing rates play key roles in distinguish the two effects.The atomic dephasing originates from atomic collisions and phase fluctuation and correlation of fields.We investigate these mechanisms in detail by employing the theory of multiplicative stochastic processes.We then decompose the probe absorption as a quantum interference term and an ATS term,and obtain the approximation models of the probe absorption contributed by the two effects.By using Akaike information criterion,we calculate the relative weights of the two effects for different coupling-field intensity and dephasing rates.Especially,the destructive quantum interference.i.e.EIT,can be enhanced by the phase correlation of fields.This method to control quantum interference provide a new possibility of flexibly manipulating the properties of media.2)We investigate the manipulation of quantum interference via atomic dephasing in all the four types of three-level systems,and verify the theory by performing a well-designed experiment.The four systems can be categorized as EIT-and ATS-type systems in dressed-state representation.We first obtain the dynamics equations of the atomic coherence between the two dressed states and a common state,and find the quantum interference can be described by a parameter which is determined by the spontaneous decay rates and dephasing rates.We then decompose the probe absorption as a quantum interference term and an ATS term,and analyze in detail the effects of atomic dephasing on the quantum interference.We finally experimentally measure the probe absorption spectra for different dephasing rates(different quantum interference strength and types),and the experiment results are well in agreement with the theoretical predictions.3)We theoretically study the preparation of superradiance lattice and the generation of edge currents in a Λ-type EIT system,and present the experimental observation of the chiral edge currents with cesium atoms at room temperature.The atomic ensemble is excited to the superradiance state by a weak probe field,and a zigzag superradiance lattice is created by applying two standing waves with different frequencies.The closed triangular loop transition in each triangle accumulates an identical or a complementary phase and thus synthesizes an effective magnetic flux,whose magnitude is determined by the relative phase between the two standing waves.In superradiance lattice,such magnetic flux leads to the generation of the edge current which is proportional to the population of the timed Dick state on the site.In the experiment,the superradiance lattice is created in a doublestanding-wave coupled cesium vapor,and the chiral edge currents are observed by measuring the phase-dependent reflectivity of the probe field on both sides of the vapor.The innovations are as follows:Ⅰ.By employing Akaike information criterion,we investigate the influences of atomic dephasing induced by phase fluctuations and correlation of fields on the quantum interference in atomic system,and find the mechanism to enhance the atomic coherence.Ⅱ.We theoretically and experimentally investigate the effects of atomic dephasing on all the four types of three-level atomic systems,and provide the possibility of flexibly manipulating the quantum interference via dephasing.Ⅲ.We synthesize the zigzag superradiance lattice in momentum space and simulate the topological edge states with hot atoms.Compared to the optical lattice in cold atoms,our scheme substantially lower the threshold of experimental investigate of chiral edge states in atoms.