[show abstract][hide abstract] ABSTRACT: We present an experimental system to generate large cross-phase modulation (XPM) in cold rubidium atoms. By using an efficient state-preparation technique in the 87Rb D1 line, an ideal four-level tripod-type atomic system is formed, which generates large cross-Kerr nonlinearity via interacting dark states in this system. The induced phase shift due to XPM for the probe beam is measured for different trigger beam intensities, which is the key to achieving conditional quantum phase gates and many other applications in quantum information processing.
Physical Review A 02/2008; 77(2). · 3.04 Impact Factor
[show abstract][hide abstract] ABSTRACT: We present our experimental and theoretical studies of multi-dark-state resonances (MDSRs) generated in a unique cold rubidium atomic system with only one coupling laser beam. Such MDSRs are caused by different transition strengths of the strong coupling beam connecting different Zeeman sublevels. Controlling the transparency windows in such an electromagnetically induced transparency system can have potential applications in multiwavelength optical communication and quantum information processing.
[show abstract][hide abstract] ABSTRACT: We demonstrate a simple, all-optical technique to prepare and determine the desired internal quantum states in multi-Zeeman-sublevel atoms. By choosing appropriate coupling and pumping laser beams, atoms can be easily prepared in a desired Zeeman sublevel with high purity or in any chosen ground-state population distributions (spin-polarized quantum-state engineering). The population distributions or state purities of such prepared atomic states can be determined by using a weak, circularly polarized probe beam due to differences in transition strengths among different Zeeman sublevels. This technique will have potential impact on quantum-information processing in multilevel atomic systems.
[show abstract][hide abstract] ABSTRACT: We investigate, both theoretically and experimentally, the phenomenon of polarization rotation of a weak, linearly-polarized optical (probe) field in an atomic system with multiple three-level electromagnetically induced transparency (EIT) sub-systems. The polarization rotation angle can be controlled by a circularly-polarized coupling beam, which breaks the symmetry in number of EIT subsystems seen by the left- and right-circularly-polarized components of the weak probe beam. A large polarization rotation angle (up to 45 degrees) has been achieved with a coupling beam power of only 15 mW. Detailed theoretical analyses including different transition probabilities in different transitions and Doppler-broadening are presented and the results are in good agreements with the experimentally measured results. Comment: 28pages, 12figures