Ultra-pure silicon chip brings quantum computing a step closer

Scientists at the University of Manchester, in collaboration with the University of Melbourne in Australia, have produced an enhanced, ultra-pure form of silicon that allows construction of high-performance qubit devices — a fundamental component required to pave the way towards scalable quantum computers.

The findings, published in the journal Communications Materials – Nature, could define and push forward the future of quantum computing.

Richard Curry, Professor of Advanced Electronic Materials at the University of Manchester, said the researchers created a critical ‘brick’ needed to construct a silicon-based quantum computer. “It’s a crucial step to making a technology that has the potential to be transformative for humankind feasible; a technology that could give us the capability to process data at such a scale, that we will be able to find solutions to complex issues such as addressing the impact of climate change and tackling healthcare challenges,” Curry said.

One of the biggest challenges in the development of quantum computers is that qubits — the building blocks of quantum computing — are highly sensitive and require a stable environment to maintain the information they hold. Even tiny changes in their environment, including temperature fluctuations, can cause computer errors.

Another issue is their scale: both their physical size and processing power. Ten qubits have the same processing power as 1024 bits in a normal computer and can potentially occupy a much smaller volume. Scientists believe a fully performing quantum computer needs around one million qubits, which provides a capability unfeasible for any classical computer.

Silicon is the underpinning material in classical computing due to its semiconductor properties and the researchers believe it could be the answer to scalable quantum computers. Scientists have spent the last 60 years learning how to engineer silicon to make it perform to the best of its ability, but in quantum computing, it has its challenges. Natural silicon is made up of three atoms of different mass (called isotopes) — silicon 28, 29 and 30. However, the Si-29, making up around 5% of silicon, causes a ‘nuclear flip-flopping’ effect causing the qubit to lose information.

Scientists from the University of Manchester have now come up with a way to engineer silicon to remove the silicon 29 and 30 atoms, making it the perfect material to make quantum computers at scale and with high accuracy.

The result — reportedly the world’s purest silicon — provides a pathway to the creation of one million qubits, which may be fabricated to the size of a pin head.

Ravi Acharya, a PhD researcher who performed experimental work in the project, explained: “The great advantage of silicon quantum computing is that the same techniques that are used to manufacture the electronic chips — currently within an everyday computer that consist of billions of transistors — can be used to create qubits for silicon-based quantum devices. The ability to create high-quality silicon qubits has in part been limited to date by the purity of the silicon starting material used. The breakthrough purity we show here solves this problem.”

The new capability offers a roadmap towards scalable quantum devices with unparalleled performance and capabilities, and holds the promise of transforming technologies in ways hard to imagine.

Professor David Jamieson, from the University of Melbourne, said the new technique opens the path to reliable quantum computers that could lead to significant changes across society, including in artificial intelligence, secure data and communications, vaccine and drug design, energy use, logistics and manufacturing.

“Now that we can produce extremely pure silicon-28, our next step will be to demonstrate that we can sustain quantum coherence for many qubits simultaneously. A reliable quantum computer with just 30 qubits would exceed the power of today’s supercomputers for some applications,” Jamieson said.

Image caption: Professor Richard Curry. Image credit: The University of Manchester.