平衡零拍探测器的噪声特性分析与实验研究

Analysis of the Noise Spectra in Balanced Homodyne Detector

平衡零拍探测器是量子光学和量子信息科学实验中的关键器件之一。本文针对典型的基于跨阻运算放大器的平衡零拍探测器,理论上详细分析了探测器的电子学噪声、散粒噪声和信噪比等输出特性;从理论分析、软件仿真和实验研究三方面分别获得了平衡零拍探测器的电子学噪声和散粒噪声功率谱,谱线线型互相吻合;实验研制的平衡零拍探测器,在分析频率2MHz处的信噪比达到了22dB,相应于电子学噪声引入的测量损耗约为0.6%,满足测量压缩态光场等量子光学实验的需求。

Balanced homodyne detector(BHD) is a key element in quantum optics and quantum information processing with continuous variables. The noise performances and the signal to noise ratio(SNR) of a BHD based on the transimpedance amplification circuit were theoretically analyzed and experimentally studied. With the typical BHD circuit, the signal gain of the circuit and the contributions of the noise sources to the noise spectra were calculated in detail. Characteristics of the electronic circuit were computational simulated and analyzed based on PSpice. With the printed-circuit-board and low noise operational amplifier of LMH6624, the experimental data on noise spectra were obtained. The experimental data are in good agreement with the theoretical calculation and simulation results. By comparing these data, the parasite capacitances on the PCB can be estimated. Under the transimpedance resistor of 6.8 k? and the capacitor of 2 pF, the maximum SNR of the developed BHD is 22 dB at the analysis frequency of 2 MHz, which contributes a measurement loss of 0.6% in the detection system. The BHD can meet the requirements of measuring squeezed state in the quantum optics experiments.