Large Cross-Phase Modulations at the Few-Photon Level

Zi-Yu Liu, Yi-Hsin Chen, Yen-Chun Chen, Hsiang-Yu Lo, Pin-Ju Tsai, Ite A. Yu, Ying-Cheng Chen, Yong-Fan Chen
2016 Physical Review Letters  
We demonstrate an efficient cross-phase modulation (XPM) based on a closed-loop double-Λ system. The property of the double-Λ medium can be controlled by changing the phases of the applied optical fields. This phase-dependent XPM scheme can achieve large phase modulations at low-light intensities without requiring cavities or tightly focusing of laser beams. With this scheme, we observe a π-level phase shift with two pulses both consisting of 8 photons in cold rubidium atoms. Such novel scheme
more » ... rovides a simple route to generate strong interactions between photons and may have potential applications in all-optical quantum signal processing.
doi:10.1103/physrevlett.117.203601 pmid:27886497 fatcat:oboxiy2lx5brngiijwlam54vie