Superfluid helium could offer a new way to tackle one of the biggest challenges in scaling up quantum computers, say researchers from the University of Surrey. The research team has introduced a conceptual design for a new type of qubit that could be much less vulnerable to errors.
Quantum computers use qubits to process information in ways that are not possible with conventional computers. One of today’s leading approaches relies on superconducting circuits, but these are extremely sensitive to electromagnetic noise and stray electrical charges – similar to the static electricity that makes hair stick to a balloon. Even tiny disturbances can cause errors and scramble the quantum information being held, making it difficult to scale up quantum computers while keeping error rates under control.
In a study published in npj Quantum Information, researchers from Surrey’s Quantum Sciences Group propose a radically different type of quantum computing hardware based on superfluid helium-3 – an unusual form of liquid helium that can flow without friction. Named the Superfluid Helium Oscillator Quantum (SHOQ) device, the proposed qubit uses charge-neutral superfluid helium, which could make it naturally immune to some forms of electromagnetic noise.
The concept is the first reported design for a superfluid-based qubit, with the team’s calculations predicting error rates around 100 times lower than conventional superconducting qubits.
Dr Priya Sharma, Daphne Jackson Fellow in Hybrid Quantum Systems at the University of Surrey’s School of Mathematics and Physics, and lead author of the study, said:
“We are not the first to think about the individual components behind this idea, but what we have done for the first time is bring them together in a microfluidic device and work out the specific details that could enable the device to function as a qubit.
“The maths tells us that it should work. We have taken what we already know about superfluid helium and quantum technologies and turned that into an educated design, with the parameters and specifications needed to build one. The next step is to make a prototype and put those predictions to the test.”
The paper outlines how the SHOQ device could be coupled with existing superconducting quantum technology, raising the possibility that superfluid qubits may work alongside, rather than replace, current hardware.
Looking further ahead, one potential application could be as a form of quantum memory, with a future version of the SHOQ device storing quantum information within a computer that uses different hardware to perform calculations.
Dr Eran Ginossar, Associate Professor at the University of Surrey’s Department of Physics and Advanced Technology Institute, and co-author of the study, said:
“We don’t necessarily need one type of qubit to do everything. Combining different quantum technologies could allow us to take advantage of the strengths of each.
“Superfluid helium gives us a fundamentally different type of quantum hardware to explore. If the predicted performance can be demonstrated experimentally, it could eventually work alongside existing superconducting technologies as part of a larger quantum system.”
The team is now looking towards building a prototype to test whether the theoretical predictions can be achieved in a real device, an effort supported by an IAA Commercialisation Fellowship awarded to Dr Priya Sharma. While the SHOQ device would need to operate at extremely low temperatures, the conditions required have already been achieved experimentally in superfluid helium-3 research.
The work was led by the University of Surrey in collaboration with Professor Jens Koch at Northwestern University in the United States, one of the researchers behind the development of the transmon – a superconducting qubit design that has become widely used in quantum computing.