All-optical π phase modulation at few photon levels
Zi-Yu Liu1*, Jun-Jie Wu1, Ite A. Yu2, Ying-Cheng Chen3, Yong-Fan Chen1
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
2Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
* presenting author:Zi Yu Liu,
We propose an efficient cross-phase modulation based on a double-Λ electromagnetically induced transparency (EIT) scheme and demonstrate a π phase shift at few photon levels in cold rubidium atoms. By changing the phases of the applied laser fields, one can control the property of the double-Λ EIT medium. This phase-dependent mechanism differentiates the double-Λ system form the conventional cross-Kerr-based system which only depends on the applied laser intensities. The proposed scheme provides a new route to generate strong nonlinear interactions between photons, and may have potential for applications in quantum information technologies.

Keywords: EIT, All-optical π phase modulation, quantum information