平衡零拍探测技术是连续变量量子信息科学研究中测量量子态量子噪声的最佳方法之一。在平衡零拍探测系统中，需要一对性能和结构尽量相同的光电探测器，以便很好地减去经典噪声，有效探测散粒噪声基准及光场噪声。根据基尔霍夫电流定律及光电二极管串联的办法，设计并制作出一种性能优良的低噪声平衡零拍探测器。该探测器从光电二极管串联节点处取出光电流相减信号，然后对信号进行放大，在对两探测器全同性要求降低的同时提高了平衡零拍探测的性能。实验结果表明，该探测器在2 MHz处共模抑制比达39 dB，能很好地满足量子信息对低噪声、线性增益及高共模抑制比的要求。

Balanced homodyne detection technology is one of the best methods for detecting the quantum noise of a quantum state in continuous variable quantum information. In the balanced homodyne detection system, a pair of detectors with the same performance are needed to effectively detect the noise limit and the quantum fluctuations of quantum states for totally eliminating classical noises. Based on the Kirchhoff current law and the scheme of photodiodes in series, a type of balanced homodyne detector with excellent capability is designed and set up. The photo-current signal is obtained from the series connection nodes of photodiodes and then amplified, thus the requirement of identity for the two detectors is degraded and the quality of the balanced homodyne detection system is improved at the same time. The experimentally measured common-mode rejection ratio (CMRR) of the detector is 39 dB at 2 MHz. The improved detector with low noise, good linear gain and high CMRR can satisfy the requirements of quantum information experiments.