Scientists have developed a new type of cryogenic computer chip capable of operating at temperatures so low that it approaches the theoretical limit of absolute zero.
This cryogenic system, called Gooseberry, 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 span just dozens.
“The largest quantum computers in the world currently operate at just 50 qubits or more,” explains quantum physicist David Reilly of the University of Sydney and Microsoft’s Quantum Laboratory.
“This small scale is due in part to the limits of the physical architecture that controls qubits.”
This physical architecture is restricted because of the extreme conditions that qubits need to perform quantum mechanics calculations.
The Gooseberry chip (red) next to a qubit test chip (blue) and a resonator chip (purple). (Microsoft)
Unlike traditional computer binary bits, which assume a value of 0 or 1, qubits occupy what is known as quantum superposition – an undefined and unmeasured state that can effectively represent 0 and 1 at the same time in the context of a larger Operation math.
This esoteric principle of quantum mechanics means that quantum computers can theoretically solve vastly complex mathematical problems that classical computers would never be able to answer (or spend years trying).
However, as with conventional technology, more is always better and, so far, researchers have been limited in how many qubits they have been able to successfully deploy in quantum systems.
One reason for this is that qubits need extreme cold levels to function (in addition to other controlled conditions), and the electrical wiring used in today’s quantum computer systems inevitably produces small but sufficient levels of heat that interrupt requirements thermal.
Scientists are looking for ways to get around this, but many quantum innovations have so far relied on bulky spinning equipment to keep temperatures stable to increase the qubit count, but this solution has its own limits.
“Today’s machines create a beautiful series of wires to control signals; they look like an inverted golden bird’s nest or chandelier,” says Reilly.
“They are beautiful, but fundamentally impractical. It means that we cannot increase the scale of the machines to perform useful calculations. There is a real bottleneck for entry and exit.”
The solution to this bottleneck could be Gooseberry: a cryogenic control chip that can operate at ‘milikelvin’ temperatures only a small fraction of a degree above absolute zero, as described in a new study.
This extreme thermal capacity means that it can stay inside the supercooled refrigerated environment with the qubits, interfacing with them and passing signals from the qubits to a secondary core that is outside in another extremely cold tank, immersed in liquid helium.
In doing so, it removes all the excess wiring and excess heat they generate, which means that contemporary qubit bottlenecks in quantum computing may soon be a thing of the past.
“The chip is the most complex electronic system to operate at this temperature,” explained Reilly to Digital Trends.
“This is the first time that a mixed signal chip with 100,000 transistors operates at 0.1 kelvin, [the equivalent to] –459.49 degrees Fahrenheit or –273.05 degrees Celsius. “
Ultimately, the team hopes that its system will allow thousands of qubits to be controlled by the cryogenic chip – an increase of approximately 20 times over what is possible today. In the future, the same type of approach can enable quantum computers at an entirely different level.
“Why not start thinking about billions of qubits?” Reilly told the Australian Financial Review. “The more qubits we can control, the better.”
While it may take some time before we see this cryogenic discovery put to use outside the laboratory, there is no doubt that we are taking a big step forward in quantum computing, experts say.
“This will be transformative in the years to come,” said Andrew White, director of the ARC Center of Excellence for Engineered Quantum Systems, who was not involved in the study but oversees quantum research in Australia.
“If all [developing quantum computers] is not using that chip, they will use something inspired by it. “
The results are reported in Nature Electronics.