Propagation of Picosecond Pulses on Superconducting Transmission Line Interconnects

TL;DR

This paper introduces a simulation method for picosecond pulse propagation in superconducting transmission lines, combining frequency-domain modeling with time-domain circuit simulation, validated by experimental results.

Contribution

A novel simulation approach integrating HFSS and Cadence Spectre models for superconducting PTLs, enabling accurate prediction of pulse propagation distances.

Findings

Nb microstrip PTLs support single-flux-quantum pulses up to 7mm

Double-flux-quantum pulses propagate up to 28mm

Simulation results agree with experimental measurements

Abstract

Interconnects are a major discriminator for superconducting digital technology, enabling energy efficient data transfer and high-bandwidth heterogeneous integration. We report a method to simulate propagation of picosecond pulses in superconducting passive transmission lines (PTLs). A frequency-domain propagator model obtained from the Ansys High Frequency Structure Simulator (HFSS) field solver is incorporated in a Cadence Spectre circuit model, so that the particular PTL geometry can be simulated in the time-domain. The Mattis-Bardeen complex conductivity of the superconductor is encoded in the HFSS field solver as a complex-conductivity insulator. Experimental and simulation results show that Nb 20 Ohm microstrip PTLs with 1um width can support propagation of a single-flux-quantum pulse up to 7mm and a double-flux-quantum pulse up to 28mm.