A Superconducting Nanowire Binary Shift Register

TL;DR

This paper introduces a superconducting nanowire binary shift register that stores and transfers digital states using circulating supercurrents, demonstrating low error rates and high-frequency operation suitable for advanced superconducting electronics.

Contribution

The paper presents a novel superconducting nanowire shift register design utilizing nanocryotrons and high-kinetic-inductance loops, enabling low-power, high-frequency digital data storage and transfer.

Findings

Achieved a bit error rate less than 10^-4.

Operates at a maximum clock frequency of 83 MHz.

Functions reliably in magnetic fields up to 6 mT.

Abstract

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.