(Tokyo,  8  December  2015) Ultrafast  and  high  efficiency  manipulation  of the quantum states  of helium with  high  power  lasers enables  the  realization of  femtosecond  two photon  Rabi  oscillations. The  research  was  reported  online  in  Nature  Photonics  on  30 November   2015   and   has   potential   applications   for room   temperature   quantum computing.

Toru  Morishita  at  the University  of  Electro-Communications,  Tokyo  (UEC,  Tokyo) and colleagues   at   Nagoya   University,   Toyama   University,   RIKEN,   Japan   Synchrotron Radiation  Research  Institute, and  Fu-Jen  Catholic  University,  Taiwan,  report  on  the successful observation of ultrafast femtosecond two photon Rabi oscillations in helium.

Interaction  of coherent  light—as  produced  by  lasers—with matter results  in  the generation of ‘superposition of quantum states’.  This  phenomenon  can  be  used  to manipulate matter  to  go  between  two  quantum states  at  ultra high  speed  at  almost 100% efficiency. This oscillation between two quantum states in different energy levels under  the  presence  of  an  oscillatory  driving  field is referred to as ‘Rabi’ oscillations. Notably, this  fundamental  physical  process  can  be  exploited  for  applications  including quantum information processing.

Inspired by the possibility of such intriguing applications, recent research is in this area is focused  on  the  possibility  of  generating multi-photon  processes. However, to-date, the generation   of   even   the simplest   two   photon   process has   required at least pico-seconds  of  time. In  terms  of  practical  applications, to  actually  manipulate  the state of matter necessitates much faster optical processes using more intense light.

On the other hand, the interaction of matter with very high intensities of light leads to changes  in  the  state  of  the  matter  itself,  with  ionization  and  other  such  competing, non-linear  phenomena  becoming  dominant, which  leads to difficulties in maintaining Rabi oscillations.

Here,  the researchers  report on the successful  manipulation  of  the quantum states of helium by  two  photon  absorption. The  experiments  consisted  of  the use  of  resonant phenomena of an intense laser field produced by an extreme ultra-violet free electron laser (EUV-FEL) and the near infra-red region of a high intensity femto second laser. See Figure 1. Specifically, Rabi oscillations were observed in the terahertz frequency range, which is three orders of magnitude faster than any previous reports. 

These  findings  are  expected  to  form  the  basic  building  blocks  of  technology  for controlling  chemical  reactions  and the room  temperature  control  of  the  quantum states of matter for quantum computing applications.

Reference Title:  Femtosecond  two-photon  Rabi  oscillations  in  excited  He  driven  by  ultrashort intense laser fields

Authors:    M.Fushitani^1,2,    C.-N.Liu³,    A.Matsuda¹,    T.Endo¹,    Y.Toida¹,    M.Nagasono², T.Togashi⁴, M. Yabashi^2,4, T. Ishikawa², Y.Hikosaka^2,5, T.Morishita⁶and A. Hishikawa^1,2*

Journal: Nature Photonics
Published on line 30 November 2015
DOI: 10.1038/NPHOTON.2015.228

1. Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8602, Japan.
2. RIKEN, SPring-8 Center,Sayo, Hyogo 679-5148, Japan.
3. Department of Physics, Fu-Jen Catholic University, Taipei 24205, Taiwan.
4. Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan.
5. Graduate  School  of  Medicine  and  Pharm aceutical  Sciences,  University  of  Toyama, Toyama 930-0194, Japan.
6. Departmentof   Engineering   Science   and   Institute   for   Advanced   Science,   The University of Electro-Communications, 1-5-1 Chofu-ga-oka, Chofu, Tokyo 182-8585, Japan.

*Corresponding author

http://www.uec.ac.jp/eng/news/announcement/2015/20151215-1.html