超导纳米线单光子探测器的概率涡旋交叉判据
Probabilistic vortex crossing criterion for superconducting nanowire single-photon detectors
摘要：
超导纳米线单光子探测器已成为一种很有前途的量子精密测量技术，从中红外到紫外频率。尽管最近的实验成功，预测模型来描述这些检测器中的检测事件是需要优化的检测指标。在这里，我们提出了一个基于单涡旋（通量量子）穿越纳米线宽度的单光子探测的概率准则。我们的模型使得暗计数和光子计数之间的检测阈值附近的连接。的有限差分计算表明，在偏置电流分布的变化，作为一个结果的光子吸收显着增加的概率单涡交叉，即使涡流势垒没有完全消失。我们估计仪器的响应函数，并表明，这个涡流隧穿过程的定时不确定性对应于一个基本的限制，在定时抖动的点击事件。我们证明了这种内在的（量子）定时抖动，量子效率，和暗计数率在TaN，WSi，和NbN超导纳米线在不同的实验条件下的贸易空间。我们的检测模型也可以解释SNSPD在较低能量下量子效率指数下降的实验观察。这导致了量子效率的脉冲宽度依赖性，并且它可以进一步用作实验测试来比较不同的检测模型。
英文摘要：
Superconducting nanowire single-photon detectors have emerged as a promising technology for quantum metrology from the mid-infrared to ultra-violet frequencies. Despite the recent experimental successes, a predictive model to describe the detection event in these detectors is needed to optimize the detection metrics. Here, we propose a probabilistic criterion for single-photon detection based on single-vortex (flux quanta) crossing the width of the nanowire. Our model makes a connection between the dark-counts and photon-counts near the detection threshold. The finite-difference calculations demonstrate that a change in the bias current distribution as a result of the photon absorption significantly increases the probability of single-vortex crossing even if the vortex potential barrier has not vanished completely. We estimate the instrument response function and show that the timing uncertainty of this vortex tunneling process corresponds to a fundamental limit in timing jitter of the click event. We demonstrate a trade-space between this intrinsic (quantum) timing jitter, quantum efficiency, and dark count rate in TaN, WSi, and NbN superconducting nanowires at different experimental conditions. Our detection model can also explain the experimental observation of exponential decrease in the quantum efficiency of SNSPDs at lower energies. This leads to a pulse-width dependency in the quantum efficiency, and it can be further used as an experimental test to compare across different detection models.
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