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We present a design for a superconducting nanowire binary shift register, which stores digital states in the form of circulating supercurrents in high-kinetic-inductance loops. Adjacent superconducting loops are connected with nanocryotrons, three terminal electrothermal switches, and fed with an alternating two-phase clock to synchronously transfer the digital state between the loops. A two-loop serial-input shift register was fabricated with thin-film NbN and achieved a bit error rate less than $10^{-4}$, operating at a maximum clock frequency of $83\,\mathrm{MHz}$ and in an out-of-plane magnetic field up to $6\,\mathrm{mT}$. A shift register based on this technology offers an integrated solution for low-power readout of superconducting nanowire single photon detector arrays, and is capable of interfacing directly with room-temperature electronics and operating unshielded in high magnetic field environments., Comment: The following article has been published in Applied Physics Letters issue 122. 10 pages, 3 figures

Absorption of light in superconducting electronics is a major limitation on the quality of circuit architectures that integrate optical components with superconducting components. A 10 nm thick film of a typical superconducting material like niobium can absorb over half of any incident optical radiation. We propose instead using superconductors which are transparent to the wavelengths used elsewhere in the system. In this paper we investigated reduced indium tin oxide (ITO) as a potential transparent superconductor for electronics. We fabricated and characterized superconducting wires of reduced indium tin oxide. We also showed that a $\SI{10}{nm}$ thick film of the material would only absorb about 1 - 20\% of light between 500 - 1700 nm., 11 pages + 10 pages appendix, 5 figures + 5 figures appendix, submitting to IOP SUST

The development of superconducting electronics based on nanocryotrons has been limited so far to few-device circuits, in part due to the lack of standard and robust logic cells. Here, we introduce and experimentally demonstrate designs for a set of nanocryotron-based building blocks that can be configured and combined to implement memory and logic functions. The devices were fabricated by patterning a single superconducting layer of niobium nitride and measured in liquid helium on a wide range of operating points. The tests show $10^{-4}$ bit error rates with above $20\,\%$ margins up to $50\,$MHz and the possibility of operating under the effect of a perpendicular $36\,$mT magnetic field, with $30\,\%$ margins at $10\,$MHz. Additionally, we designed and measured an equivalent delay flip-flop made of two memory cells to show the possibility of combining multiple building blocks to make larger circuits. These blocks may constitute a solid foundation for the development of nanocryotron logic circuits and finite-state machines with potential applications in the integrated processing and control of superconducting nanowire single-photon detectors., Submitted for publication in the Applied Physics Letters special issue "Advances in Superconducting Logic", 8 pages, 5 figures

The authors present the use of a commercially available fixed-angle multiwavelength ellipsometer for quickly measuring the thickness of NbN thin films for the fabrication and performance improvement of superconducting nanowire single photon detectors. The process can determine the optical constants of absorbing thin films, removing the need for inaccurate approximations. The tool can be used to observe oxidation growth and allows thickness measurements to be integrated into the characterization of various fabrication processes.