Integrated superconducting nanobridge fast readout electronics for single photon detector arrays

该项目将为超导单光子探测器SSPD阵列开发一种紧凑的低温读出器，并评估其商业化的适用性。读出将基于超导单通量量子（SFQ）电路，其中输入信号被转换成一系列可用于数字信号处理的量化脉冲。SFQ电路的构建块将是包含超导纳米桥的回路，这些超导纳米桥充当显示约瑟夫森效应的弱连接。SSPD阵列有许多应用：作为量子密钥分发的快速、高效、低噪声检测器，作为量子计算的组件和增强的量子成像。SSPD阵列系统商业化的主要障碍是缺乏合适的读出电子设备，该读出电子设备能够处理大量信号，而不会对检测器冷级产生显著的热负荷。SFQ读出器提供低功耗解决方案，可在适销对路的机械冷却系统中实现多个像素。用于SSPD阵列读出的纳米桥SFQ电路是一种新的、未被证明的替代传统隧道结SFQ电路的方法，具有主要的单层制造、更小的器件尺寸和与SSPD阵列集成在同一芯片上的潜力。纳米桥电路将使用电子束光刻和在洁净室设备中沉积的超导薄膜的剥离来制造。初步工作将需要确定各种尺寸的纳米桥的电参数，以便可以开发和测试完整的电路模型。一个完整的SFQ器件设计可以由NPL的项目合作伙伴进行制造、测试和评估。为了将来自SSPD的快脉冲耦合到SFQ，需要一个输入线圈电路来放大电流。我们将设计和制造合适的多匝输入线圈与适当的终端电阻。这些将由NPL的项目合作伙伴进行测试。然后，我们将制造完全集成的设备（输入线圈和SFQ设备），这些设备将在NPL进行测试和评估，最初使用外部电输入脉冲，但最终使用来自格拉斯哥大学项目合作伙伴提供的设备的真实的SSPD信号。

The project will develop a compact, cryogenic readout for superconducting single photon detector SSPD arrays and assesstheir suitability for commercialisation. The readout will be based on a superconducting single flux quantum (SFQ) circuitwhere an input signal is converted into a series of quantised pulses that can be used for digital signal processing. Thebuilding block of the SFQ circuits will be loops containing superconducting nanobridges that act as weak links displayingthe Josephson effect.SSPD arrays have many applications; as a fast, high efficiency, low noise detector for quantum key distribution, as acomponent in quantum computing and for enhanced quantum imaging. The major hurdle to commercialisation of SSPDarray systems is the lack of suitable readout electronics able to process a large number of signals without significant heatloading of the detector cold stage. SFQ readout offers a low power solution, enabling multiple pixels in a marketable,mechanically cooled system. Nanobridge SFQ circuits for SSPD array readout are a new, undemonstrated alternative toconventional tunnel junction SFQ circuits, with the advantage of predominantly single layer fabrication, smaller device sizeand potential for integration on the same chip as the SSPD array.The research that will be carried out University College London will involve the actual fabrication of the nanobridge SFQcircuits. The nanobridge circuits will be fabricated using e-beam lithography and lift-off of superconducting thin filmsdeposited in a cleanroom facilty. Initial work will be be needed to determine the electrical parameters of nanobridges ofvarious dimensions so that a full circuit model can be developed and tested. A complete SFQ device design can then befabricated and tested and assessed by the project partners at NPL. In order to couple the fast pulse from an SSPD to theSFQ an input coil circuit will be needed to amplify the current. We will design and fabricate suitable multiturn input coils withappropriate terminating resistors. These will be tested by the project partners at NPL. We will then fabricate fully integrateddevices (input coil and SFQ devices) which will be tested and evaluated at NPL, initially with external electrical inputpulses, but eventually with real SSPD signals from devices supplied by project partners at Glasgow University.