地面与微重力环境下冷原子量子磁性的精密测量

Precise measurements of quantum magnetism of cold atoms in ground and microgravity environment

冷原子是利用激光制冷、蒸发制冷等冷却手段将原子制备到接近绝对零度的状态.作为当前量子物理的一个重要国际前沿,冷原子物理已经发展到探索、研究、测量原子内部的自旋自由度.对其内部自旋自由度的超精细结构所呈现的丰富量子磁性的精密测量,无论是对基础物理,或是新技术的运用,无疑都有着非常重要的作用.而借助于微重力环境的优势,创造新的极端条件,冷原子实验系统可获得地面无法达到的pK量级的超低温以及长时间的精密测量,量子磁性的操控与精密测量可以突破地面重力的限制而达到新的参数区域.本文综述了地面与微重力环境下冷原子实验原理、装置、方案,不同磁量子数塞曼态间转移、磁性相变,以及飞行时间成像与相衬成像.就其精密测量,着重阐述了在微重力下使冷原子继续深度冷却,和使用非破坏相衬成像测量手段这两方面.

Cold atom states are prepared by laser cooling,evaporation cooling and other cooling methods to cool down the atoms close to almost absolute zero in temperature.As a popular research frontier of quantum physics,cold atom physics has been developed to explore,study and measure the spin degrees of freedom in atoms.The precise measurement of the rich quantum magnetism presented by the hyperfine structure of the internal spin freedom is undoubtedly of great significance to basic physics and the innovation of new technologies.With the advantages of microgravity environment and the creation of new extreme conditions,cold atom experimentalists can achieve long-time precision measurement and ultralow temperature of p K level which is not viable on the ground.The manipulation and precision measurement of quantum magnetism can break through the gravitational limit and reach new parameter regions.In this paper,we review the principles,devices and schemes of cold atom experiments in ground and microgravity environment,the transfer between Zeeman states with different magnetic quantum numbers,magnetic phase transition,time-of-flight imaging and phase contrast imaging.As for the precise measurement,two aspects are emphasized:the deep cooling of atoms under microgravity and the use of non-destructive phase contrast imaging.