| 研究実績の概要 |
The objective is to study a system of 2 Rydberg atoms, closed enough (typ. 0.5-1 um) for their electronic orbitals to overlap. The plan is (1) to trap Rubidium (Rb) and Cesium (Cs) in submicron-sized optical tweezers, (2) to cool these atoms to < 1 uK (enough to remove oscillation of the atoms in the traps), and (3) to excite the atoms to Rydberg state and perform spectroscopy.
(1) is completed. Laser-cooled cloud of Rb and Cs atoms have been obtained. Trapping and fluorescence imaging of single Rb atoms in an array of up to 800 holographic tweezers optical tweezers have been achieved using a specially-designed high-performance microscope objective giving a tweezers size of only 0.6 micrometer. Using advanced holographic techniques, two atoms can now be prepared as close as 1.2 micrometer, and a scheme to reach 0.9-1 micrometer is under investigation.
(2) is completed. The atom motion has been successfully reduced close to the motional quantum ground-state along the radial and axial direction of the tweezers by applying the Raman-sideband cooling technique.
(3) is completed. A new ultrafast (10 ps) excitation scheme, relying on resonant excitation of a short-lived intermediate state, has been realized and led to high efficiency preparation of the atoms in Rydberg state. A clear effect of the dipole-dipole interaction between single atoms have been observed on a nanosecond-timescale. We observed a coherent interaction-driven oscillation, giving rise to a conditional phase shift, which can be used to generate an ultrafast Rydberg quantum gate, in a regime unexplored so far.
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