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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

Ionic gating is a powerful technique for tuning the physical properties of a material via electric field-induced charge doping, but is prone to introduce extrinsic disorder and undesired electrochemical modifications in the gated material beyond pure electrostatics. Conversely, reversible, volatile and electrostatic modulation is pivotal in the reliable design and operation of novel device concepts enabled by the ultrahigh induced charge densities attainable via ionic gating. Here we demonstrate a simple and effective method to achieve reversible and volatile gating of surface-sensitive ultrathin niobium nitride films via controlled oxidation of their surface. The resulting niobium oxide encapsulation layer exhibits a capacitance comparable to that of non-encapsulated ionic transistors, withstands gate voltages beyond the electrochemical stability window of the gate electrolyte, and enables a fully-reversible tunability of both the normal-state resistivity and the superconducting transition temperature of the encapsulated films. Our approach should be transferable to other materials and device geometries where more standard encapsulation techniques are not readily applicable., Comment: Main text: 11 pages, 6 figures; Supplementary: 8 pages, 6 figures

We integrate niobium nitride superconducting nanowire single-photon detectors (SNSPDs) on thin-film lithium niobate (LN) photonic waveguides. Further development of this technology may push towards more complex circuits and functionalities on this already promising platform.

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.

There has been a demand for a scalable superconducting memory technology for cryogenic computing for some time. This demand has proven difficult to satisfy due to the simultaneous need for high speed operation, low power consumption, and high density, all while maintaining cryogenic and SFQ compatibility. In an effort to satisfy this demand, we have developed a simple memory cell based on our prior work with nanowire-based memories. Due to the memory cell’s reliance on kinetic inductance, the cell can be scaled to almost any size. The cell has been designed specifically such that it can easily form into an array simply by arranging in a 2D pattern. This design eliminated the need for external addressing circuitry. This new cell, when operated in isolation and without the heater, performs very well with predicted bit error rates around 10−17. However, preliminary array tests show that while the memory operates, the predicted error rates rise to 1.5 × 10−3. We believe that this issue is predominantly due to the hTron-channel kinetic inductance dramatically changing upon the application of the row-select heaters. This issue might be addressed by designing the cell to compensate for the change in kinetic inductance when the heater is activated. If this remedy proves to be effective, then this memory would enable the development of compact and scalable memory arrays.

In this work we present an affordable approach for developing a photolithography system with the capability of producing samples with a minimum feature size down to 30 /spl/mu/m while staying within a budget of $5000.00. Such a system will provide a cost-effective method for creating micro-scale biomedical devices. To improve the system robustness, a dose control system was developed to compensate for fluctuations in the power of the light source. To demonstrate the system's performance, a set of inertial focusing devices were fabricated.