Experiental studies on quantum measurements using entanglement

我们实验研究了周期性极化MgO:LiNbO_3波导中通过光学参量放大产生的皮秒压缩脉冲的时间特性。用平衡同差检测器测量了压缩脉冲和本振之间的各种时间延迟的噪声方差。测量到的延迟依赖是不对称的，这种不对称表明压缩脉冲的相位啁啾与本振脉冲的相位啁啾不同。结果表明，利用本振的脉冲整形可以改善所观察到的压缩现象。通过在平衡同差检测中使用临时形本振，我们观察到-5.0 dB以下的压缩噪声水平。据我们所知，这是波导挤压器获得的最高水平。

We experimentally investigate the temporal characteristics of picosecond squeezed pulses generated via an optical parametric amplification in a periodically poled MgO:LiNbO_3 waveguide. The noise variances for the various time delays between the squeezed pulse and a local oscillator are measured using a balanced homodyne detector. The measured delay dependence is asymmetric, and this asymmetry indicates that the phase chirping of the squeezed pulse is different from that of the local oscillator pulse. We show that the observed squeezing can be improved by using the pulse shaping of the local oscillator. By using a temporally shaped local oscillator in a balanced homodyne detection, we obverved the squeezing of -5.0 dB below the shot noise level. To our best knowledge, this is the highest level obtained for waveguide squeezers.