2016 Fiscal Year Annual Research Report
Developing a fiber optical quantum interface using trapped atoms and nanofiber based photonic crystal cavity
| Project/Area Number |
15H05462
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
Nayak K.Prasanna 電気通信大学, フォトニックイノベーション研究センター, 特任准教授 (70551042)
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| Project Period (FY) |
2015-04-01 – 2019-03-31
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| Keywords | Quantum Optics / Nanophotonics / Optical Nanofiber / Cavity QED / Quantum Information |
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| Outline of Annual Research Achievements |
The purpose of the research is to develop a fiber optical quantum interface using nanofiber based photonic crystal cavity. In this project we will develop optical tweezer based single-atom trap near the nanofiber cavity so that deterministic quantum state-transfer between single atom and photons can be realized.
In FY2015, we have succeeded in trapping single atoms in optical tweezer. However, loading the trapped single atoms to the nanofiber trap was not achieved.
In FY2016, we have implemented two developments for trapping atoms near nanofiber. We have succeeded in fabricating 300 nm diameter nanofibers with high transmission over 99% and also modified the fiber holding structure to minimize the nanofiber vibration inside the vacuum chamber. In spite of these developments, we have not yet succeeded in loading single atoms to the nanofiber trap. We attribute this issue to the interaction of trapped atoms with the nanofiber surface. However in FY2016, we have successfully fabricated centimeter-long cavity on the nanofiber which can operate in both Purcell and strong-coupling regimes of cavity QED with high transmission. Also we have succeeded in installing such cavity into vacuum chamber and stabilizing the cavity mode to the atomic line.
The objective for FY2017 is to investigate cavity QED experiments with free falling laser-cooled atoms and the centimeter-long nanofiber cavity. Based on the atom-cavity signal first we will resolve the issues with trapping single atoms on the nanofiber. Then cavity QED experiments will be performed using trapped single atoms.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
In FY2016, we have modified the fiber holding structure to minimize the nanofiber vibration inside the vacuum chamber. Then we have attempted optical tweezer based single-atom trap near a 300 nm diameter nanofiber. However, we have not yet succeeded in loading single atoms to the nanofiber trap.
We attribute this issue to the interaction of trapped atoms with the nanofiber surface. We have realized serious reduction of atom density when the laser-cooled atoms are overlapped with the nanofiber. We attribute such effects to modified nanofiber surface due to atoms sticking to the nanofiber surface. We believe that such effects can be mitigated by heating up the nanofiber by sending 10-100 uW of laser through the guided mode. We will investigate such effects while observing the laser induced fluorescence spectrum of atoms measured through the nanofiber guided modes.
Another issue for successful transport of atoms from optical tweezer to the nanofiber trap, is the atom temperature in the tweezer. So we have also attempted for Raman cooling of single atom in the optical tweezer. In order to carry out such experiments first we performed Raman spectroscopy of trapped single atoms. However, we have realized several issues for efficient optical pumping and atomic state detection. So we are planning to combine microwave spectroscopy setup for further flexibility.
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| Strategy for Future Research Activity |
The research plan for FY2017 are the followings.
1- Installation of high quality nanofiber cavity in to the vacuum chamber. In FY2015 and FY2016 we have realized some degradation of the cavity transmission while installation. So we are planning to construct a clean booth equipped with HEPA filter around the vacuum chamber to maintain the cavity transmission during installation.
2- Cavity QED experiment with free falling laser-cooled atoms. In order to avoid additional complications in loading single atoms to nanofiber trap, first we plan to investigate cavity QED experiments with free falling laser-cooled atoms. For this experiments we will be using the centimeter-long nanofiber cavity which can operate in both Purcell and strong-coupling regimes of cavity QED (achieved in FY2016). The experiment will be performed by measuring the transmission spectrum of nanofiber cavity using a weak probe laser through the guided mode. In the presence of resonant single atoms around the nanofiber the transmission spectrum will show a dip at the resonance and the width of the dip will depend on the atom-cavity coupling strength. This is the so-called vacuum-Rabi splitting.
3- Cavity QED experiments with trapped single atoms. Based on the atom-cavity signal we will investigate the loading of single atoms to the nanofiber trap. We will carry out further experiments with trapped single atom and fiber-guided single photons.
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Research Products
(7 results)
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[Presentation] Nanofiber quantum photonics2017
Author(s)
K. P. Nayak, R. Yalla, J. Keloth, and K. Hakuta
Organizer
SPIE Photonic West, OPTO, Slow Light, Fast Light, and Opto-Atomic Precision Metrology X
Place of Presentation
San Francisco, California, United States
Year and Date
2017-01-28 – 2017-02-02
Int'l Joint Research / Invited
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