Nanobridge SQUIDs as multilevel memory elements

TL;DR

This paper demonstrates a superconducting SQUID-based multilevel memory device capable of reliably storing eight discrete flux states at cryogenic temperatures, utilizing novel flux control mechanisms for potential quantum computing applications.

Contribution

It introduces a field-assisted writing scheme and a phase slip mechanism enabling multilevel flux state control in SQUIDs, advancing superconducting memory technology.

Findings

Achieved eight distinct vorticity states readout at zero magnetic field.

Developed a phase slip-based switching mechanism for flux control.

Demonstrated potential for deterministic flux state manipulation.

Abstract

With the development of novel computing schemes working at cryogenic temperatures, superconducting memory elements have become essential. In this context, superconducting quantum interference devices (SQUIDs) are promising candidates, as they may trap different discrete amounts of magnetic flux. We demonstrate that a field-assisted writing scheme allows such a device to operate as a multilevel memory by the readout of eight distinct vorticity states at zero magnetic field. We present an alternative mechanism based on single phase slips which allows to switch the vorticity state while preserving superconductivity. This mechanism provides a possibly deterministic channel for flux control in SQUID-based memories, under the condition that the field-dependent energy of different vorticity states are nearby.