图 1  成像光路示意图. 其中符号的含义为FC: 光纤耦合头, PBS: 偏振分束器, F1—F4: 透镜, OB: 5×成像物镜, CCD: 电荷耦合器件.

Fig. 1.  Imaging setup for noise measurements. The meaning of each symbol: FC: Fiber Collimator, PBS: polarization beam splitter, F1–F4: lens, OB: 5× imaging objective, CCD: charge coupled device.

图 2  原子OD随成像光光强的变化关系. 蓝点为实验数据, 红线为高斯公式拟合结果

Fig. 2.  The relationship between atomic OD and imaging light intensity. The blue point is the experimental data, and the red line is the fitting result of Gaussian formula.

图 3  不同温度下原子数涨落Var(N)与平均原子数$\left\langle N \right\rangle $的关系. 红色为高温${T=}{0.7}{{T}}_{\rm{F}}$, 蓝色为低温${T=}{0.3}{{T}}_{\rm{F}}$, 红色虚线是对高温数据密度较低时的拟合, 斜率为0.55, 这个数值反映了系统真实的散射截面为理论值的55%

Fig. 3.  The relationship between the fluctuation of atomic number and the average atomic number at different temperatures. Red is high temperature ${T=}{0.7}{{T}}_{\rm{F}}$, blue is low temperature ${T=}{0.3}{{T}}_{\rm{F}}$, red dotted line is the fitting of high temperature data with low density, and the slope is 0.55, which reflects that the real scattering cross section of the system is 55% of the theoretical value.

图 4  不同温度下原子密度与密度涨落的比较 (a)${T}{=}{0.}{3}{{T}}_{\rm{F}}$; (b)${T}{=}{0.7}{{T}}_{\rm{F}}$. 图中左侧为原子密度分布, 右侧为密度涨落

Fig. 4.  Comparison of atomic density and density fluctuation at different temperatures: (a)${T}{=}{0.}{3}{{T}}_{\rm{F}}$; (b)${T}{=}{0.7}{{T}}_{\rm{F}}$. In figure (a) (b), the distribution of atomic density is on the left, and the density fluctuation is on the right.

图 5  不同温度下原子密度与密度涨落的空间分布. 图中红线为原子密度分布, 蓝线为密度涨落分布

Fig. 5.  Spatial distribution of atomic density and density fluctuation at different temperatures. The red line is the atomic density distribution and the blue line is the density fluctuation distribution.

图 6  密度涨落Var$ (N)/\langle N\rangle $随温度的变化. 其中虚线为理论计算, 蓝点为实验测量结果, 此时BIN = 8

Fig. 6.  Density fluctuation with temperature. The blue point is the experimental result, where BIN = 8 and the dotted line is the theoretical curve.