利用平衡零拍探测测量电磁诱导透明(EIT)介质中探测场的正交振幅和正交相位噪声谱。在平衡零拍探测系统中通过调节压电陶瓷来改变本振光的光程从而改变本振光与探测光的相对相位，进而测量不同相位对应的探测光的噪声分量。实验中电磁诱导透明介质中探测光与耦合光耦合导致探测光噪声的增大，发现在耦合光不同失谐下对探测光不同正交分量引入的额外噪声是不同的，同时得到了探测光噪声与耦合光功率及分析频率的关系。

Balanced homodyne detection is used to measure the quadrature amplitude and quadrature phase noise spectra of the probe field in electromagnetically induced transparency (EIT) medium. Through adjusting the voltage of the piezoelectric ceramic transducer, the optical path of the local light is changed so that the relative phase of the local light and the probe light in the balanced homodyne detection is adjusted. Then the noise components of the probe light with different phases are measured. It is observed that the coupling of the probe light and the coupling light leads to the increase of the noise of the probe light in eletromagnetically induced transparency medium. It is found that the induced extra noises of different quadrature components of the probe field are different for different detuning values of the coupling light. Simultaneously, the relationship between the noise of the probe field, the power of the coupling light and analysis frequency is obtained.