A superfluid helium qubit could cut quantum errors roughly a hundredfold

Error rates around 100 times lower than those of today’s superconducting qubits: that is the prediction attached to a proposed quantum bit built from superfluid helium-3 at the University of Surrey. Dr Priya Sharma, a Daphne Jackson Fellow in hybrid quantum systems, and Dr Eran Ginossar, an associate professor of physics, designed the device with Prof Jens Koch of Northwestern University, and no one has built it yet. The team’s pitch is that a charge-neutral fluid sidesteps the electromagnetic noise that limits the superconducting qubits in use now.

The figure comes from calculation and modelling, which Sharma is open about, saying the mathematics indicates the design should work and that the prototype is the next step toward testing it.

The SHOQ device and its charge-neutral fluid

The design is called the Superfluid Helium Oscillator Quantum device, or SHOQ. Surrey’s announcement of the work, also carried by Newswise, says it uses superfluid helium-3, a liquid that flows without friction and, crucially, carries no electrical charge. Superconducting qubits, the type used in most large quantum processors today, are charged circuits, so stray electromagnetic noise couples into them and scrambles the fragile quantum state. A neutral fluid should shrug off much of that interference, and that shielding is the mechanism behind the predicted hundredfold reduction. The team frames the advantage as one of principle rather than engineering polish: if the qubit has no charge to couple to, the dominant noise source in superconducting designs has far less to grip.

The team’s earlier preprint of the proposal describes the hardware: a cylindrical cell with a Josephson weak link, a nanoaperture through which the superfluid flows between two helium reservoirs, and an elastic plate that responds to pressure changes. Energy sloshes between the weak link and the plate, and the quantized oscillations form the qubit’s discrete states. The preprint places the operating point near half a millikelvin, below the superfluid transition of helium-3-B, with micron-sized dimensions.

The npj Quantum Information abstract and the 100-fold figure

The peer-reviewed version, titled “Towards a micromechanical qubit based on quantized oscillations in superfluid helium,” appeared in npj Quantum Information with Sharma, Koch and Ginossar as authors. Its abstract calls the device a charge-neutral alternative to superconducting qubits, micron-sized, with millisecond-scale coherence time and operation in the millikelvin range needed to maintain superfluidity. The abstract as read does not itself print the 100-fold comparison; that number is attached to the work in Surrey’s announcement, which states that the calculations predict error rates around 100 times lower than conventional superconducting qubits.

That distinction decides how the figure should be read. The comparison is against superconducting qubits, it is a prediction from theory, and the baseline is whatever error rate those devices show, not a measurement taken on a SHOQ chip. Quantum Zeitgeist’s account likewise frames the design as theoretical predictions that still need experimental validation.

Hybrid role, Northwestern’s Koch and the prototype stage

Ginossar does not describe the device as a replacement for superconducting hardware. A single qubit type does not have to do everything, he said, and combining different quantum technologies could let a machine take advantage of each type’s strengths. Surrey’s announcement points to two uses for the device, neither of which depends on beating superconducting hardware everywhere: integration alongside existing superconducting circuits, and quantum memory.

The component ideas existed separately before this work, in earlier helium-3 and superconducting-circuit research, and the Surrey contribution is the assembly. Sharma said that what the team has done for the first time is bring them together in a microfluidic device and work out the specifics needed for operation, which gave Surrey a specification a laboratory can build to. The next step, in her words, is to make a prototype and put the predictions to the test.

Money for that step is already in place. An IAA Commercialisation Fellowship awarded to Sharma supports prototype development, according to the university. Koch’s involvement matters for credibility with the superconducting community, because Surrey’s announcement notes that he helped develop the transmon superconducting qubit, the standard design the SHOQ is measured against.

The cold is not a new obstacle in this proposal. Surrey says the temperatures the device needs have already been reached in earlier helium-3 research, so the experimental challenge lies in fabricating the nanoscale weak link and plate and reading out their quantum states, not in reaching an unprecedented temperature. Coherence is the other test: the abstract’s millisecond-scale target is long enough to run gate operations, but the proposal describes the device on paper, so fabrication defects and readout electronics have yet to be tested against the predicted figures.

A built SHOQ qubit, measured against a superconducting qubit on the same task, would have to show something close to a hundredfold drop in errors to confirm the prediction, and only the prototype Sharma’s team is now building can supply that measurement.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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