Coherent Control of Single-Photon Absorption and Reemission in Two-Level Atoms (Invited)

Jia, Wenzhi, Wang +1 more

Shanchao Zhang, Chang Liu, Shuyu Zhou +3 more

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 the time domain.

Gerard J Milburn

Shengwang Du

Shanchao Zhang, Chang Liu, Shuyu Zhou +3 more

With narrow-band heralded single photons, we demonstrate that the single-photon absorption and reemission processes in a two-level atomic ensemble can be coherently controlled by shaping the incident photon temporal waveform.

Shanchao Zhang

Exploring coherent photon-atom interaction at quantum level has become more and more important in modern quantum physics and quantum information science. In this PhD thesis research work, we established two cold 85Rb atoms ensemble in 2-dimensional dark-line magneto-optical trap with OD more than 100 and produced long coherence time (~1us) heralded single photons via spontaneous four-wave-mixing process with full temporal waveform control from one of the cold atomic ensemble. With this system, optical precursor of a single photon was observed for the first time, which verifies that information carried by a single photon cannot be transferred faster than light speed in vacuum even in the quantum world. This closed the longtime debate on the true speed of the information carried by a single photon. Single photon reemission timing in a two-level atomic system was the first time been controlled on-demand. With this technique, the quantum timing order of the single photon absorption and reemission was first directly observed in time domain. This technique can also be further used in the field of efficient single atom excitation that is desired for the quantum network. Finally, a series of work were conducted to improve the quantum optical memory efficiency in cold atomic ensemble. We obtained the highest single-photon storage efficiency of about 50%, which brings the quantum light-matter interface closer to practical quantum information applications. Multi-bin and multi-channel optical memory were also exploited in the following work.