Scientists have developed a new kind of cryogenic computer chip that can function at temperatures so cold that it is nearing the theoretical limit of absolute zero.
Called Gooseberry, this cryogenic system lays the foundation for what could be a revolution in quantum computing – allowing a new generation of machines to perform calculations with thousands of qubits or more, while today’s most advanced devices contain only dozens.
“The world’s largest quantum computers currently operate with just 50 qubits,” explains quantum physicist David Reilly of the University of Sydney and Microsoft’s Quantum Laboratory.
“This small scale is partly due to limitations of the physical architecture that power the qubits.”
That physical architecture is limited due to the extreme conditions that qubits need to perform quantum mechanical calculations.
The gooseberry chip (red) next to a qubit test chip (blue) and resonator chip (purple). (Microsoft)
Unlike the binary bits in traditional computers, which take a value of 0 or 1, qubits occupy what is known as the quantum superposition – an undefined and unmeasured state that can effectively represent both 0 and 1 in the context of a larger mathematician operation.
This esoteric principle of quantum mechanics means that quantum computers can theoretically solve hugely complex mathematical problems that classical computers could never answer (or try for years).
As with conventional technology, more is always better, and to date, researchers have been limited in the number of qubits they have been able to successfully implement in quantum systems.
One reason for this is that qubits need extreme cold to function (among other controlled conditions), and the electrical wiring used in today’s quantum computing systems inevitably produces small but sufficient levels of heat that disrupt thermal requirements.
Scientists are looking for ways to get around that, but until now many quantum innovations have relied on devising bulky wiring systems to keep the temperature stable to increase the number of qubits, but that solution has its own limitations.
“Today’s machines make a wonderful array of wires to control the signals — they look like an inverted gold-plated bird’s nest or a chandelier,” says Reilly.
“They’re beautiful, but fundamentally impractical. It means we can’t scale up the machines to perform useful calculations. There’s a real bottleneck between input and output.”
The solution to that bottleneck could be Gooseberry – a cryogenic control chip that can operate at ‘millikelvin’ temperatures just a fraction of a degree above absolute zero, as described in a new study.
That extreme thermal capacity means that it can sit in the super-cold cooled environment with the qubits, communicate with them, and pass signals from the qubits to a secondary core sitting outside in another extremely cold tank, immersed in liquid helium.
In doing so, it removes all the excess wiring and the excess heat they generate, meaning today’s qubit bottlenecks in quantum computers could soon be a thing of the past.
“The chip is the most complex electronic system to operate at this temperature,” Reilly explains to Digital Trends.
“This is the first time that a mixed signal chip with 100,000 transistors will operate at 0.1 Kelvin,” [the equivalent to] –459.49 degrees Fahrenheit, or –273.05 degrees Celsius. “
Ultimately, the team expects their system would allow control of thousands of qubits through the cryogenic chip – about a 20-fold increase from what is possible today. In the future, the same kind of approach could enable quantum computing on a completely different level.
“Why don’t you start thinking about billions of qubits?” Reilly told me Australian Financial Review. “The more qubits we can control, the better.”
While it may take some time to see this cryogenic breakthrough being put to practical use outside of the lab, there is no doubt that we expect a major step forward in quantum computing, experts say.
“This will be transformational in the years to come,” Andrew White, the director of the ARC Center of Excellence for Engineered Quantum Systems, who was not involved in the study but oversees quantum research in Australia, told ABC News.
“As everyone [developing quantum computers] don’t use this chip, they will use something inspired by it. “
The findings are reported in Nature electronics.