《12 Coherent Control of Single-Photon Absorption and Reemission in a Two-Level Atomic Ensemble》.pdf

week ending PRL 109, 263601 (2012) P H Y S I C A L R E V I E W L E T T E R S 28 DECEMBER 2012 Coherent Control of Single-Photon Absorption and Reemission in a Two-Level Atomic Ensemble Shanchao Zhang,1 Chang Liu,1 Shuyu Zhou,1 Chih-Sung Chuu,2 M. M. T. Loy,1 and Shengwang Du1,* 1Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People’s Republic of China 2Physics Department, National Tsing Hua University, Hsinchu 30013, Taiwan, Republic of China (Received 7 August 2012; published 27 December 2012) We demonstrate coherent control of single-photon absorption and reemission in a two-level cold atomic ensemble. This is achieved by interfering the incident single-photon wave packet with the emission (or scattering) wave. For a photon with an exponential growth waveform with a time constant equal to the excited-state lifetime, we observe that the single-photon emission probability during the absorption can be suppressed due to the perfect destructive interference. After the incident photon waveform is switched off, the absorbed photon is then reemitted to the same spatial mode as that of the incident photon with an efficiency of 20%. For a photon with an exponential decay waveform with the same time constant, both the absorption and reemission occur within the waveform duration. Our experimental results suggest that the absorption and emission of a single photon in a two-level atomic ensemble may possibly be manipulated by shaping its waveform in th