Development of series SQUID array with on-chip filter for TES detector

A cold preamplifier based on superconducting quantum interference devices(SQUIDs)is currently the preferred readout technology for the low-noise transition edge sensor(TES).In this work,we have designed and fabricated a series SQUID array(SSA)amplifier for the TES detector readout circuit.In this SSA amplifier,each SQUID cell is composed of a first-order gradiometer formed using two equally large square washers,and an on-chip low pass filter(LPF)as a radiofrequency(RF)choke has been developed to reduce the Josephson oscillation interference between individual SQUID cells.In addition,a highly symmetric layout has been designed carefully to provide a fully consistent embedded electromagnetic environment and achieve coherent flux operation.The measured results show smooth V-Φcharacteristics and a swing voltage that increases linearly with increasing SQUID cell number N.A white flux noise level as low as 0.28μφ;/Hz;is achieved at 0.1 K,corresponding to a low current noise level of 7 pA/Hz;.We analyze the measured noise contribution at mK-scale temperatures and find that the dominant noise derives from a combination of the SSA intrinsic noise and the equivalent current noise of the room temperature electronics.     

一种基于单磁通量子的超导纳米线单光子探测器阵列的读出电路

超导纳米线单光子探测(Superconducting Nanowire Single Photon Detector, SNSPD)阵列可以实现单光子成像或高速单光子探测，如何有效对SNSPD阵列进行信号读出是实现SNSPD阵列的关键技术之一，本工作设计了一种基于超导单磁通量子(Single Flux Quantum, SFQ)的SNSPD阵列读出电路，该读出电路能够实现对阵列中SNSPD的地址分频，实验采用的核心编码电路利用4位二进制码对包含8个SNSPD的阵列进行编码，使用了基于SFQ的异或逻辑单元、D触发器、分路器和约瑟夫森传输线等标准单元，总计使用191个约瑟夫森结，采用两级流水线设计，仿真中最高可在19.4GH2的时钟频率下工作，功耗为42.1μW,在液氦环境下完成了编码电路的功能测试，验证了编码功能的正确性。     

泡型图的条件匹配排除

一个图的条件匹配排除数是最少的边的数量,使得删除这些边形成的图既没有孤立点,也没有完美匹配和几乎完美匹配.本文给出了泡型图的条件匹配排除数和它的所有最优集.     

Photon-counting chirped amplitude modulation lidar system using superconducting nanowire single-photon detector at 1550-nm wavelength

We demonstrate a photon-counting chirped amplitude modulation(CAM) light detection and ranging(lidar) system incorporating a superconducting nanowire single-photon detector(SNSPD) and operated at a wavelength of 1550 nm.The distance accuracy of the lidar system was determined by the CAM bandwidth and signal-to-noise ratio(SNR) of an intermediate frequency(IF) signal. Owing to a short dead time(10 ns) and negligible dark count rate(70 Hz) of the SNSPD, the obtained IF signal attained an SNR of 42 d B and the direct distance accuracy was improved to 3 mm when the modulation bandwidth of the CAM signal was 240 MHz and the modulation period was 1 ms.     

2001年上海市第十届中学生数学知识应用竞赛（初赛试题）

初赛试题共有十五题,其中1-10题,每题10分,11-15题每题16分,满分为180分. 1.某工厂制造小长方体零件,然后通过焊接得到一个大长方体零件.现把6个小长方体     

聚[1,3-双(对羧基苯氧基)丙烷-癸二酸](20:80)-替莫唑胺长效缓释微球的制备及药物缓释性能的研究

合成了聚[1,3-双(对羧基苯氧基)丙烷-癸二酸](20:80)(CPP-SA),并利用喷雾干燥法制备了替莫唑胺Temozolomide(TMZ)-(CPP-SA)缓释微球。通过对TMZ的不同包合方法的研究,确定了喷雾干燥法作为制备此类微球的最佳方法,获得了良好的药物缓释曲线。结果表明,微球对药物释放曲线平稳,释放时间长,能超过800h。为抗肿瘤药物TMZ的体内植入提供了有意义的理论依据。     

2000年上海市“第九届“中学生数学知识应用竞赛(初赛试题)

一、有块长为120cm,宽为90cm的矩形薄铁皮材料,现要剪一个长方体的展开图,做一个长方体的模型.(不考虑剪拼的耗损) 　　1.要使长方体体积最大,并求出体积最大值.……     

The 0–π Phase Transition in Epitaxial NbN/Ni_(60)Cu_(40)/NbN Josephson Junctions

We fabricate high quality superconductor/ferromagnet/superconductor(SFS) Josephson junctions using epitaxial NbN/Ni_(60)Cu_(40)/NbN trilayer heterostructures. Both experimental measurements and theoretical calculations of the ferromagnet layer thickness dependence of the Josephson critical current are performed. We observe the damped oscillation behavior of the critical current as a function of the ferromagnetic layer thickness at 4.2 K,which shows a 0–π phase transition in this type of magnetic Josephson junction. Clear 0– and reverse –0 phase transitions occur around the Ni_(60)Cu_(40) thicknesses of 3.2 and 6.7 nm. Numerical calculations based on the quasi-classical Usadel equation and the Green function fit well with the experimental results. Compared with the dirty limit, the intermediate regime without the dead layer gives better fit for our SFS Josephson junctions because of the epitaxial structure. Both of the 0-and -phase junctions show the ideal magnetic field dependence with a Fraunhofer-like pattern at 4.2 K.     

Fabrication and characterization of all-Nb lumped-element Josephson parametric amplifiers

Josephson parametric amplifiers (JPAs) with nearly quantum-limited noise performance have become indispensable devices for the measurements of superconducting quantum information. We have developed an all-Nb lumped-element flux-driven JPA operating in the three-wave mixing mode. Our Nb-based JPA comprises Nb/Al-AlO_x/Nb Josephson junctions, a parallel-plate capacitor with SiO₂ dielectric sandwiched between two Nb layers, a bottom coplanar waveguides layer, and a top Nb wiring layer. We experimentally demonstrate a 20 dB gain over a 190 MHz bandwidth, a mean 1 dB compression of -123 dBm, and near quantum-limited noise performance. This fabrication process can be further used to design impedance transformed parametric amplifiers for multiple-qubit readout.     

基于铅铟合金线的SFQ多芯片超导互连方法研究

用基于铅铟合金线的引线键合(WB)工艺对单磁通量子(SFQ)多芯片的超导互连方法进行了研究,将铅含量75%,铟含量25%的铅铟合金线制备成WB线材,用超声楔形焊工艺成功实现SFQ芯片I/O接口焊盘的超导互连.拉力测试表明室温下铅铟合金线键合强度与同线径金线相当,优于同线径铝线;用开尔文四端法测量了铅铟合金线互连的多级超导转变温度以及线材与超导芯片之间的接触电阻,结果表明该铅铟合金线的超导转变温度为6.63 K,当温度降低至6.63 K或更低时,铅铟合金线的线阻以及线材与SFQ芯片I/O接口焊盘的接触电阻为0,实现了超导互连;并通过热冲击实验验证该WB结构具有优异的热稳定性.