The Research On The Quantum Control Of Optics And Atom Medium

In the past two decades, it was addressed that the nonlinear conversion can be greatly enhanced using the quantum coherence in atomic medium. There are many ways to prepare atomic coherence. One is to use electromagnetically induced transparencey (EIT) for generation of atomic coherence. Another approach is to prepare atomic spin wave (or collective atomic excitation) through the Raman conversion process. Atomic spin wave due to its potential applications for quantum information processing has attracted a great deal of interest.Recently, the atomic spin wave acts as a seed to the Raman amplification process for enhanced Raman conversion. An efficient Raman conversion scheme with coherent feed-back have been demonstrated experimentally. The coversion efficiency of the scheme is as high as 50% for the Stokes field and 30% for the anti-Stokes field with pump field power as low as a few hundreds of microwatt in both pulsed and continuous wave modes. With the advantage of high conversion based on the Raman process, there are some application in the quantum metrology. Our detailed theoretical research is presented as follow:1. A new Raman process can be used to realize efficient Raman frequency conversion by coherent feedback at low light intensity. We present a theoretical model to describe this enhanced Raman process, termed as cascade correlation-enhanced Raman scattering. That is a Raman process injecting by a seeded light field which is correlated with the initially prepared atomic spin excitation and driven by the quasi-standing-wave pumping field, and the process are repeated until the Stokes intensities are saturation. Such an enhanced Raman scattering may find applications in quantum information, nonlinear optics, and optical metrology due to its simplicity.2. The quantum correlation of light and atomic collective excitation can be used to compose an SU(1,1)-type hybrid light-atom interferometer, where one arm in the optical SU(1,1)-type interferometer is replaced by the atomic collective excitation. The phase-sensing probes include not only the photon field but also the atomic collective excitation inside the interferometer. For a coherent squeezed state as the phase-sensing field, the phased sensitivity can approach the Heisenberg limit under the optimal conditions. We also study the effects of the loss of light field and the dephasing of atomic excitation on the phase sensitivity. This kind of active SU(1,1)-type interferometer can also be realized in other systems, such as circuit quantum electrodynamics in microwave systems, which provides a different method for basic measurement using the hybrid interferometers.