Atom Manipulation Based On Optical Cavity Quantum Electrodynamics

Cavity quantum electrodynamics (Cavity QED), as a branch of modern physics closely related to atomic physics and quantum optics, mainly focus on the research of the interaction between light field and atoms confined system. By studying the quantum phenomena inside such small world, people can profoundly understand the dynamic process of interaction between atoms and photons. In the last decades, because of the progress in both the optical micro-cavity of high quality and atom cooling and trapping, the interaction between atoms and photons has reached what is called strong-coupling range in micro-wave and optical domain. In this case, an entangled atom-photon-cavity system is established and this novel system is widely used either for fundamental quantum physics or quantum information Science, such as quantum state preparation, quantum measurement, quantum computation, and quantum networks, etc.Yet, all such progresses would thank the achievements in atomic physics in the last decades, specially the atom manipulations by lasers. The most important step of realizing strong-coupling range is to control the individual atoms. With the development of various controlling technologies of cold atoms, single atom has been effectively cooled and controlled and can beidentified with certainty by optical dipole trap. However, the key issue of realizing atom manipulation is the laser techniques. The quality of lasers, including the noise and the linewidth, and the control of lasers directly determine how well the atoms can be controlled. The work of this thesis is mainly focus on the characters of diode lasers, the double MOT system for Cesium neutral atom trapping, and the single quanta measurement based on the optical micro-cavity.There are four main parts in this thesis. In the first part, we describe the basic characteristics of diode laser for atom cooling and trapping. Then, we showed the phase noise properties of diode laser under external feedback condition. Moreover, we introduce the realization of Cesium atoms cooling and trapping by double MOT and the measurement of corresponding parameters in third part. Finally, we discuss briefly the basic scheme of measuring of the interaction of single-atom and single photon and make an outlook for possible future prospects.The main works and results we have accomplished are shown as followings:1. The linewidth of diode laser are measured by two different methods and compared their characters with each other. The optimum work condition of external cavity diode laser has been studied and we make a set of tunable external cavity diode laser with Littrow configuration;2. Analyze the effect on diode laser noise by external optical feedback and measure the phase noise of LD in self-mixing interference by means of external cavity amplitude-phase converter. The measurement uncertainties are resolved and we obtain quantitively the phase noise with cavity scanning. The experiment results show that under certain condition, the phase noise of LD can be decreased about 20dB. This work is important for analyzing the effect of light field interacting with atoms, especially for the effect on controlled atom's radiation by probe field with some large phase jitter;3. Automatic controlling system by computer programs has been establishedfor laser cooling and trapping and cavity QED experiment. The laser and magnetic fields can be controlled by the acoustic-optical modulators and the electronic-controlled logic gate respectively;4. An ultrahigh-vacuum chamber and its vacuum pumps system are designed and constructed for cavity QED. Vacuum degree of \.0x\0~6 Pa and 8 x i(r8 Pa can be maintained for a long period;5. A finely optical system has been designed and constructed for our Cesium atom double MOTs with improved trapping beams. The MOT in ultrahigh-vacuum chamber is achieved by continuously transferring atoms. Each cooling beam intensity is around M.lmW I cm1, detuning is about -\2MHz , magnetic field gradient is nearly -\2MHz . The effective temperature of 41 ± 4pK in UHV MOT is successfully obtained;6. The polarization gradient cooling has been achieved with 2.5mW /cm2 of the molasses-beam intensity, detuning nearly -50MHz and maintaining time of about 2ms. Under these conditions, the temperature of the cold atoms sample reaches about \0^K;7. Under such experiment condition, the principal methods towards single-atom manipulation are presented, including micro-cavity controlling, laser frequency chain locking and some methods for single-atom detection.