Fig. 1. Diagrammatic illustration of the quantum Poincaré sphere and Stokes parameters.量子化的庞加莱球和斯托克斯参量图示

Fig. 2. Apparatus required to measure four Stokes parameters. PBS, polarizing beam splitter; and , half-and quarter-wave plates, respectively; the plus and minus signs imply that an electrical sum or difference has been taken; SA, Spectrum analyzer. 四个斯托克斯参量的测量装置. PBS, 偏振分束棱镜; 和 分别是半波片和四分之波片; 加号和减号分别代表电流信号相加减; SA, 频谱分析仪

Fig. 3. Apparatus used to produce the bright polarizationsqueezed beam.明亮偏振压缩光合成装置

Fig. 4. Schematic of experimental setup.实验装置图

Fig. 5. Parametric gain versus pump power, where green (red) solid dots denote the experimental results of amplified (deamplified) gain. The solid lines represent the theoretical results.参量增益随泵浦光功率的变化, 其中绿(红)色实点是参量放大(缩小)的实验结果. 实线是理论拟合结果

Fig. 6. Noise power when scanning the local beam phase. The spectrum analyzer’s center frequency is 2 MHz with RBW = 100 kHz and VBW = 500 Hz. 扫描本地光相位时得到的噪声. 谱仪中心频率为2 MHz, 分辨率带宽(RBW)为100 kHz, 视频带宽(VBW)为500 Hz

Fig. 7. Measured noise results for different Stokes parameters. The results on the left are the measured variance spectra of Stokes parameters normalized to quantum noise limit. The results on the right are the corresponding diagrammatic illustration of the Stokes parameters’ variance ellipsoid, and the blue ellipsoid is the noise ball, and these ellipses are the noise projections at each plane. The red dashed circles represent the noise of the coherent state and the blue solid circles show the squeezing. (a) Squeezing for Stokes parameter ; (b) Squeezing for Stokes parameter ; (c) Squeezing for Stokes parameter . 不同斯托克斯参量的噪声测量结果. 其中左图是测量的斯托克斯参量的噪声谱, 已归一化到标准量子噪声基准. 右图是与之对应的噪声分布球及投影噪声分布, 其中蓝色椭球体代表噪声球, 椭圆表示噪声球投影到各个面上的噪声分布. 红色虚线表示相干光对应的噪声, 蓝色实线表示偏振压缩光　(a) 压缩; (b) 压缩; (c) 压缩

Table 1. Factors of effecting squeezing from the OPA and the detection system.