Squeezed light—light with quantum noise lower than shot noise in some quadratures and higher in others—can be used to improve the sensitivity of precision measurements. In particular, squeezed light sources based on nonlinear optical crystals are being used to improve the sensitivity of gravitational wave detectors. In optomechanical squeezers, the radiation-pressure-driven interaction of a coherent light field with a mechanical oscillator induces correlations between the amplitude and phase quadratures of the light, which induce the squeezing. However, thermally driven fluctuations of the mechanical oscillator’s position make it difficult to observe the quantum correlations at room temperature and at low frequencies. Here, we present a measurement of optomechanically squeezed light, performed at room temperature in a broad band near the audio-frequency regions relevant to gravitational wave detectors. We observe sub-Poissonian quantum noise in a frequency band of 30–70 kHz with a maximum reduction of 0.7 ± 0.1 dB below shot noise at 45 kHz. We present two independent methods of measuring this squeezing, one of which does not rely on the calibration of shot noise.

压缩光（在某些正交图中量子噪声低于散粒噪声，而在另一些正交图中具有更高的量子噪声的光）可用于提高精密测量的灵敏度。特别地，基于非线性光学晶体的挤压光源被用于提高重力波检测器的灵敏度。在光机械压缩器中，相干光场与机械振荡器的辐射压力驱动相互作用会在光的振幅和相位正交之间引起相关性，从而引起压缩。然而，机械振荡器位置的热驱动波动使得很难在室温和低频下观察量子相关性。在这里，我们介绍了光机械压缩光的测量，在室温下在与重力波检测器相关的音频区域附近的宽带中执行。我们观察到30-70 kHz频带内的亚泊松量子噪声，与45 kHz的散粒噪声相比，最大降低了0.7±0.1 dB。我们提出了两种独立的方法来测量这种压缩，其中一种不依赖散粒噪声的校准。