Integrated superconducting nanobridge fast readout electronics for single photon detector arrays

点击翻译按钮获取中文摘要

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.