Brisbane-based Analog Quantum Circuits is building microwave components a fraction of the width of a human hair, solving one of the hidden bottlenecks in scaling superconducting quantum computers.

Company: Analog Quantum Circuits (Brisbane, QLD)
Quantum technology: Superconducting on-chip microwave components - Josephsonjunction circulators and related devices
Research partners: University of Southern Queensland;
Originating research: From the ARC Centre of Excellence for Engineered Quantum Systems (EQUS), University of Queensland
Investor: Seed round led by Uniseed
Application: Enabling hardware for scaling superconducting quantum computers; supplying the global quantum hardware industry
End user / industry application: Quantum hardware suppliers and superconducting quantum computer manufacturers - on-chip superconducting microwave components, developed using facilities at the University of Queensland (UQ) and the University of Southern Queensland (UniSQ).

Most quantum computing headlines focus on qubits - how many a system has, how accurately they operate, how stable they are. But every one of those qubits needs to talk to the outside world, and the wiring that lets them do so is rapidly becoming a bottleneck.

A modern superconducting quantum computer - including the machines built by Google and IBM - can look like a forest of cables and microwave components hanging inside a dilution refrigerator, a complexity that poses a fundamental challenge to scaling the technology.

Components called circulators, which route weak microwave signals while protecting fragile quantum states from thermal noise, are each the size of a matchbox. A useful quantum computer will need millions of qubits and millions of circulators talking to them. The geometry simply doesn’t work.

Brisbane-based Analog Quantum Circuits (AQC) is rebuilding circulators from first principles. Founded in 2022 by University of Queensland researchers Tom Stace and Arkady Fedorov, AQC is Australia’s first superconducting quantum technology start-up. AQC R&D draws on more than a decade of theoretical and experimental research within the Australian Research Council’s Centre of Excellence for Engineered Quantum Systems (EQUS).

AQC’s initial proof-of-concept devices were based on a passive on-chip superconducting microwave circulator built from a loop of three Josephson junctions. In published results in Physical Review Letters and Physical Review Research, AQC has demonstrated circulation fidelity above 97% with very low insertion loss (meaning minimal signal degradation) in a small device just tens of micrometres across, around 1,000 times smaller than commercial circulators.

That kind of miniaturisation is exactly what scaling quantum hardware demands.

Today’s superconducting systems will run out of physical space inside their refrigerators long before they run out of qubits. AQC’s components could let quantum computer manufacturers integrate the routing electronics directly onto the same chip as the qubits themselves.

The work is being done in cryogenic dilution refrigerators that operate at minus 273 degrees Celsius - just 0.015 degrees above absolute zero, and far colder than outer space - because quantum hardware is exquisitely sensitive and even ambient electrical noise at room temperature is around 10,000 times too loud.

AQC is backed by a $3 million investment led by Uniseed, with additional funding from the Australian Government’s Advanced Strategic Capability Accelerator (ASCA) program.

In partnership with the University of Southern Queensland, AQC commissioned, and is now collocated at the brand-new, $4M Quantum Cryo Lab (QC Lab) based at the UniSQ Springfield Campus. The QC Lab is funded by the Queensland Government’s Quantum Commercialisation Infrastructure Program (QCIP), as part of their $76 million investment in Quantum and Advanced Technologies.

AQC will sell into the international quantum hardware market. Its components are designed to be useful to anyone building a superconducting quantum computer and it is steadily expanding its product range as the field’s appetite for scalable, integrated microwave hardware grows.

“A quantum computer needs qubits. But you can’t scale a quantum computer if every qubit needs a matchbox-sized component bolted to the side of it.

By shrinking the footprint of critical microwave components by a factor of 1,000 or more, we’re removing one of the practical engineering barriers to
building machines with millions of qubits.

That’s the kind of foundational work that will enable fault tolerance - and we’re proud to be doing it here in Brisbane”

— Tom Stace, CEO, Analog Quantum Circuits