超导单光子探测器件直流特性研究

超导单光子探测技术是基于超薄超导薄膜的非平衡态热电子效应的一种新型的单光子探测方法。超导单光子探测器(SNSPD)的计数率可达到GHz,时间抖动小于100ps,因而在未来量子通信系统中有着广阔的应用前景。介绍了NbN超导单光子探测器件的工作原理和器件超导性能测试系统;测试了超导单光子探测器件的电阻-温度、电流-电压等特性。并对测试结果进行了分析和讨论。     

铌/铝SNSPD的光耦合结构和性能表征

对铌/铝超导纳米线单光子探测器(SNSPD)的光耦合结构和性能表征进行了研究。通过溅射与剥离的方法制作了超薄铌/铝SNSPD,设计了带有激光准直器的光耦合结构和封装方法,并搭建了可靠的低温测试系统。在700m K下表征了SNSPD的直流特性,得到了单光子响应脉冲和1550nm波长下的探测效率,并研究了探测效率和暗计数率与偏置电流的关系。     

基于Nb/Al材料结构的超导纳米线单光子探测器的光学表征（英文）

本文主要研究了作为可见光和近红外光波段Nb基单光子探测器.在本文中概述了Nb+Al结构的超导纳米线单光子探测器(SNSPD)的制备,并对制备出的SNSPD器件进行了直流表征,测试了其超导转变温度,并从中选取了直流特性良好的样品进行了光学表征.当单光子探测器被一个直流偏置在其临界电流以下并接近临界电流值时,激光器发出的1550nm波段的光子脉冲到达单光子探测器,使其产生电学信号.20nm厚的SNSPD不能对单光子产生反应;5nm厚的SNSPD可以探测单个光子,并且计算了其系统探测效率.     

超导单光子探测技术

单光子探测是弱光测量技术的核心,在量子信息、物理、生物、化学和天文学领域具有关键性的作用。传统以光电倍增管或雪崩二极管为基础的单光子探测器的低灵敏度和高暗计数限制了信噪比的提高,低计数率限制了测量速度和动态范围。本文综述了以超导材料作为光敏感器件的单光子探测技术,其量子效率、暗计数率和计数率远高于传统的单光子探测器,它们的出现势必给单光子测量相关学科带来巨大影响。     

超导单光子探测技术

单光子探测是弱光测量技术的核心,在量子信息、物理、生物、化学和天文学领域具有关键性的作用。传统以光电倍增管或雪崩二极管为基础的单光子探测器的低灵敏度和高暗计数限制了信噪比的提高,低计数率限制了测量速度和动态范围。本文综述了以超导材料作为光敏感器件的单光子探测技术,其量子效率、暗计数率和计数率远高于传统的单光子探测器,它们的出现势必给单光子测量相关学科带来巨大影响。     

超导纳米线单光子探测系统的时间抖动

超导纳米线单光子探测(SNSPD)器件具有较低的时间抖动特性,可以实现低误码率的QKD和高精度的激光测距。文中对超导纳米线单光子探测系统的时间抖动进行了详细的分析和测量,分析了SNSPD系统各部分对系统抖动的贡献。使用时间相关的单光子计数技术(TCSPC)和示波器的抖动分析软件,分别测量了SNSPD系统的时间抖动,比较了两种方法的优劣。在两种测量方法下,系统总的时间抖动分别约为42ps和31ps,计算后得到单光子探测器件的抖动约为25ps。发现放大器的性能对系统时间抖动影响明显。通过使用不同放大器比较分析了测量得到的时间抖动。     

单光子探测器性能对量子密钥分发系统的影响

根据量子密钥分发协议的原理和单光子探测器的工作模式系统分析了单光子探测器性能对量子密钥分发系统影响的物理模型,给出了单光子探测器暗计数和量子效率对系统筛选码率和量子误码率等指标产生影响的计算公式,并通过对各类量子密钥分发系统的比较,推导出了适用于一般量子密钥分发系统的普适结果。结果表明,在同等条件下采用较少的探测时间门可以提高量子密钥分发系统的性能。     

光量子信息利器——超导纳米线单光子探测器

利用超导宏观量子效应与环境电磁场的相互作用,超导探测器可以实现量子极限灵敏度探测。超导纳米线单光子探测器(SNSPD)具备高探测效率、低暗计数等优异的性能,已经在量子信息、深空通信、激光雷达等领域得到了广泛的应用,并为中国"九章"光量子计算原型机、量子密钥分发等领域达到国际领先水平提供了核心探测技术支持。文章简述了SNSPD的基本原理,对其性能、制冷技术、应用以及常见的问题等进行了介绍,并对未来发展做了展望。     

具有光学结构的超导纳米线吸收效率的仿真

超导纳米线单光子探测器(SNSPD)的系统探测效率由纳米线与光子的耦合效率、纳米线的吸收效率以及纳米线吸收光子后能产生电压脉冲的本征量子效率决定。设计了一种带有防反射层、谐振腔、布拉格反射镜等结构的SNSPD。利用COMSOL软件的射频模块对这种新型结构的SNSPD进行了仿真,结果表明具有光学结构的SNSPD将有助于提高系统探测效率。     

基于热敏超导边界转变传感的单光子探测技术

单光子探测是实现光量子信息处理的关键技术之一。基于热敏超导边界转变传感的单光子探测技术以其独有的极低的暗计数率、极高的量子探测效率和极强的光子数分辨能力而倍受关注。对比于其他的几种单光子探测技术,如光电倍增管、工作于盖革模式的雪崩二极管和超导纳米线等,本文将从其探测原理、实验样品制备和信号采集处理方法等方面出发,对基于热敏超导边界转变传感单光子探测技术研究的历史、现状进行综述,进而展望其未来可能的发.     

Intrinsic timing jitter of superconducting nanowire single-photon detectors

We report on an experimental investigation of the timing jitter (TJ) in a fiber-coupled detection system based on a superconducting nanowire single-photon detector (SNSPD). We used a picosecond pulsed laser and fiber delay lines to generate subsequent optical pulsed pairs in each period and measured the TJ between the pulses. Because only the interval time between two pulses in each period was interested, we did not need to know the absolute time of every pulse. Therefore, the TJ from laser and trigger signal can be removed. In order to estimate the intrinsic TJ of SNSPD, we analyzed the TJ caused by time distribution of optical pulse, electronic components, readout noise, kinetic inductance and dispersion in fiber channel. Finally, we obtained the intrinsic TJs for two kinds of detectors considering these impacts.     

基于电热模型的SNSPD 响应过程模拟与时间抖动分析

超导单光子探测器(SNSPD) 具有高探测效率, 低时间抖动、 低暗计数率、 高计数率等优点. 文章通过对纳米线电热过程的建模, 分析了纳米线的电热响应过程, 探讨了负载电阻、 偏置电流和动态电感对 SNSPD 响应时间的影响, 结合蒙特卡洛方法来模拟研究了纳米线空间不均匀性对于SNSPD 时间抖动的影响, 结果表明随着纳米线空间不均匀性的增加, 纳米线的时间抖动不断增加, 并求出了典型的时间抖动约为7.73 ps     

面向窄线宽超导纳米线单光子探测器的电子束曝光技术

超导纳米线单光子探测器是新型超导电子器件,因其具有高探测效率、低暗计数及低时间抖动等优势,在量子信息、激光雷达等方面已得到广泛的应用.目前主流超导纳米线单光子探测器主要工作在1.5_m 以下的可见光和近红外波段.中红外波长的红外探测技术在基础科学、医学、日常生活以及军事等广泛领域发挥着重要作用,中红外单光子探测器可以使得中红外波段探测技术进入量子极限灵敏度.根据超导纳米线单光子探测器探测机理,超窄线宽的纳米线条可以提升超导纳米线单光子探测器在中红外波长的灵敏度.电子束曝光技术是目前实现超导纳米线单光子探测器纳米线线条加工的主流技术,电子束抗蚀剂种类繁多,面向超窄线宽超导纳米线单光子探测器器件的制备需求,对两款抗蚀剂进行性能测试表征,和窄纳米线制备尝试.根据负性电子束抗蚀剂MaN-2401在制备窄线宽时的显著优点,优化工艺,利用其成功制备出50nm 线宽超导纳米线单光子探测器并成功实现了2000nm 的单光子响应.     

Photon number resolvability of multi-pixel superconducting nanowire single photon detectors using a single flux quantum circuit

Superconducting nanowire single-photon detectors (SNSPDs) are typical switching devices capable of detecting single photons with almost 100% detection efficiency. However, they cannot determine the exact number of incident photons during a detection event. Multi-pixel SNSPDs employing multiple read-out channels can provide photon number resolvability (PNR), but they require increased cooling power and costly multi-channel electronic systems. In this work, a single-flux quantum (SFQ) circuit is employed, and PNR based on multi-pixel SNSPDs is successfully demonstrated. A multi-input magnetically coupled DC/SFQ converter (MMD2Q) circuit with a mutual inductance M is used to combine and record signals from a multi-pixel SNSPD device. The designed circuit is capable of discriminating the amplitude of the combined signals in accuracy of Φ₀/M with Φ₀ being a single magnetic flux quantum. By employing the MMD2Q circuit, the discrimination of up to 40 photons can be simulated. A 4-parallel-input MMD2Q circuit is fabricated, and a PNR of 3 is successfully demonstrated for an SNSPD array with one channel reserved for the functional verification. The results confirm that an MMD2Q circuit is an effective tool for implementing PNR with multi-pixel SNSPDs.     

Performance of superconducting nanowire single-photon detector with the fan coupling antenna array

The performance of superconducting nanowire single-photon detector （SNSPD） involving niobium nitride with the fan coupling antenna array is analyzed. The SNSPD has a high detection efficiency and counting rate. Hydrogen silsesquioxane and niobium nitride are filled in the gold grating deposited on the substrate in which the fan coupling antenna arrays are embedded. By changing the position of the fan coupling antenna array, the maximum area of optical intensity is obtained and the photon collection efficiency is increased by 26.5 times. The detection efficiency of SNSPD is improved without changing the detection speed. These parameters are important for designing a practical single-photon detector,     

Experimental evidence for anisotropic response of a driven vortex lattice

We present kinetic inductance measurements in current driven Josephson junction arrays. Measurements performed with circular coils indicate that this technique is very sensitive to the vortex mobility. Results obtained with anisotropic detection coils provide experimental evidence for the anisotropic response of a driven vortex lattice. Anisotropic behavior is obtained when rising the temperature or the mean vortex velocity as indicated by the loss of the superconducting shielding capability, first in the direction of vortex motion and then in the perpendicular direction.     

超导纳米线单光子探测器

利用磁控溅射、电子束光刻和反应离子刻蚀等微加工技术,开展了超导纳米线单光子探测器(SNSPD)的研究.通过对SNSPD的设计和制备工艺参数的优化,成功制备出了高质量的SNSPD.单光子检测实验表明,制备的SNSPD对660 nm波长的光信号,系统检测效率可达30%,对1550 nm波长光信号,最大系统检测效率为4.2%.在平均暗计数小于10 c/s的情况下,系统检测效率大于20%(660 nm)和3%(1550 nm). 关键词： 单光子 氮化铌 纳米线 探测器     

Fabrication of superconducting Nb N meander nanowires by nano-imprint lithography

Superconducting nanowire single photon detector(SNSPD), as a new type of superconducting single photon detector(SPD), has a broad application prospect in quantum communication and other fields. In order to prepare SNSPD with high performance, it is necessary to fabricate a large area of uniform meander nanowires, which is the core of the SNSPD. In this paper, we demonstrate a process of patterning ultra-thin Nb N films into meander-type nanowires by using the nanoimprint technology. In this process, a combination of hot embossing nano-imprint lithography(HE-NIL) and ultraviolet nano-imprint lithography(UV-NIL) is used to transfer the meander nanowire structure from the NIL Si hard mold to the Nb N film. We have successfully obtained a Nb N nanowire device with uniform line width. The critical temperature(Tc) of the superconducting Nb N meander nanowires is about 5 K and the critical current(Ic) is about 3.5 μA at 2.5 K.