Modelling the transfer function of two-dimensional SQUID and SQIF arrays with thermal noise

TL;DR

This paper develops a theoretical model for 2D SQUID and SQIF arrays at 77 K, emphasizing thermal noise effects, and demonstrates scaling laws and optimization strategies for their transfer functions.

Contribution

It introduces a simplified scaling model for 2D SQUID arrays, accounting for thermal noise, and explores optimization of transfer functions and effects of parameter spreads.

Findings

Thermal noise significantly influences array behavior.

A simple scaling law relates 1D and 2D SQUID array voltages.

Optimal bias current improves maximum transfer function.

Abstract

We present a theoretical model for 2D SQUID and SQIF arrays with over-damped Josephson junctions for uniform bias current injection at 77 K. Our simulations demonstrate the importance of including Johnson thermal noise and reveal that the mutual inductive coupling between SQUID loops is of minor importance. Our numerical results establish the validity of a simple scaling behaviour between the voltages of 1D and 2D SQUID arrays and show that the same scaling behaviour applies to the maximum transfer functions. The maximum transfer function of a 2D SQUID array can be further optimised by applying the optimal bias current which depends on the SQUID loop self-inductance and the junction critical current. Our investigation further reveals that a scaling behaviour exits between the maximum transfer function of a 2D SQUID array and that of a single dc-SQUID. Finally, we investigate the voltage response of 1D and 2D SQIF arrays and illustrate the effects of adding spreads in the heights and widths of SQUID loops.