Real-time Measurement And Trapping Of Single Atoms In A Strongly Coupled Atom-Cavity System

The radiation characteristic of the atom depends on not only its internal structure, but also the external environment. By changing the electromagnetic field around the mode distribution density, the interaction between atom and light can be enhanced significantly. For example, when a single atom is in a single mode of optical cavity, the interaction between single atoms and a single mode field can be realized; When the coupling strength between them is much larger than the interaction between atom and the other external modes, it becomes the typical structure of the system of Cavity Quantum electrodynamics (Cavity Quantum electrodynamics, Cavity QED) in the strong coupling region. This system is an ideal system for studying the coupling between single atoms and cavity field.It has been applied in the research of quantum physics and quantum information processing as well as quantum internet and so on. But the accurate manipulation of single atoms in the optical cavity is a necessary step to achieve the above goals.This research of this thesis is based on the strong coupling cavity QED experiment system. In experiment, single atoms transported by free falling are strongly coupled to a single mode of our high finesse cavity and are trapped inside the cavity. By combining Monte Carlo simulation and our experimental results together, we can not only optimize the experiment parameters, but also determine the temperature of the atoms in the magneto-optical trap. Based on the strongly coupling atom-cavity system, i.e. single atom "microscope", atom trajectory in the higher order transverse mode has been observed and the position can be determined with sub-micron scale accuracy. In addition, the statistical property of the atomic beam is investigated by a large number of atom events recorded by the cavity and the bunching effect of the beam is detected. To coherently manipulate single atoms inside the cavity and extend the interaction time, single atoms trapping by in-axial magic wavelength of standing wave dipole trap is realized and the life time of single atoms inside the cavity can be raised to about 7 ms by cavity cooling. Moreover, atom trapping based on the nanofiber is studied both in theory and experiment. Finally, a scheme of beating standard quantum limit is present by combing the non-classical states and non-Gaussian detection, which has potential for improving accuracy of measurement of atom positions in our experiment.In these research works, innovative works are listed as follows:1. By the way of free falling to transport atoms to the micro cavity, the strongly coupling between atom and cavity is realized in experiment. The whole process of the experiment is simulated by Monte Carlo method and it agrees with the experimental datas very well. Based on both of the simulation and experiment, a new method of measuring temperature is developed and necessary for our new cavity as guidance to the design of new cavity parameters.2. Based on the optical microcavity as a single atomic microscope, the transmission spectrum of cavity is observed when single atoms strongly interact with the cavity. The measuring accuracy of the single atom position can reach the submicron level. And the statistics of the atomic beam provided by MOT is investigated and it follows the bose-Einstein statistics distribution and present bunching effect like thermal light.3. Using Far off-resonant magic wavelength of standing wave dipole trap in the cavity, the single atoms can be trapped inside the cavity for long time, which can be increased further by cavity cooling.We can not only realize the state is not insensitive trapping in the cavity, but also observe the atom in real time.4. The study of atom trapping based on nanometer fiber opened up a new road for the manipulation of the atom. It is important for the application of quantum communication owing to its advantage of strong extensibility and high transmission efficiency as well as miniaturization.5. We studied a scheme based on optical cavity to relize the ultrasensitivity and resolution measurement by using the non-classical light (squeezed vacuum state) and non-gaussian measurement (number of photons can distinguish detection and parity).It shows great potential for quantum strategies to achieve enhanced quantum measurement. And we try to achieve a higher accuracy in measurement of atomic motion or get some new nonlinear phenomena of the system by using the squeezed vacuum state light field in our experiment.