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中国物理学会期刊

基于布洛赫振荡的非亚反冲6Li原子的动量转移

CSTR: 32037.14.aps.75.20251397

Momentum transfer of non-subrecoil 6Li atoms based on Bloch oscillations

CSTR: 32037.14.aps.75.20251397
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  • 原子干涉仪可以实现反冲频率的高精度测量, 对于确定精细结构常数至关重要. 本文在^6\rmLi冷原子团中基于布洛赫振荡发展了一种大动量转移技术, 通过将原子装载至高阱深的光晶格中并对布洛赫激光频率进行绝热啁啾, 在远高于反冲温度的条件下实现了40倍反冲动量的大动量转移, 在该动量下转移原子数目可达5\times 10^6. 研究还发现, 在高温条件下初速度与光晶格加速方向一致的原子更容易被加速. 该大动量转移技术有望大幅度提高^6\rmLi原子反冲频率的测量精度, 为后续在^6\rmLi原子干涉仪中实现精细结构常数的高精度标定提供重要参考.

     

    Atom interferometer enables high-precision measurement of recoil frequency, which is crucial for determining the fine structure constant. Large momentum transfer (LMT) based on Bloch oscillations in atom interferometers can significantly enhance the measurement precision of the recoil frequency. Typically, applying Bloch oscillations to an atomic ensemble requires the atoms to be cooled within the first Brillouin zone. However, deep cooling of lithium atoms is challenging, making it difficult to directly apply Bloch oscillations. Therefore, this paper develops an LMT technique based on Bloch oscillations in a relatively high-temperature ensemble of 6Li atoms. By constructing a deep potential optical lattice, the high-temperature atoms can be efficiently loaded into the lattice. Subsequently, the optical lattice is adiabatically chirped to suppress interband transitions of the atoms, thereby enabling them to accelerate with the lattice. Although the efficiency of a single Bloch oscillation decreases under the tight-binding approximation, this method simultaneously relaxes the temperature requirements of the LMT technique. Consequently, we achieve a large momentum transfer of 40 recoil momentum at 80 μK (far above the recoil temperature), with the number of transferred atoms reaching up to 5×106. Subsequent analyses of the atomic momentum spectrum before and after the Bloch oscillations reveal that due to Doppler broadening, the atomic momentum shows a continuous distribution between the initial momentum and the target momentum, which limits the momentum transfer efficiency. It is found that for a fixed optical lattice depth and pulse duration, the momentum distribution of atoms participating in the Bloch oscillations is independent of the number of oscillations. Furthermore, atoms with initial velocities aligned with the acceleration direction of the optical lattice are more easily accelerated. This LMT technique is expected to substantially enhance the measurement precision of the 6Li atomic recoil frequency, providing an important reference for subsequent high-precision calibration of the fine structure constant using 6Li atom interferometers.

     

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