Sun. Dec 5th, 2021

Through Microsoft’s partnership with the university, Professor David Reilly and colleagues have invented a device that works 40 times colder than deep space, to directly control thousands of qubits, the building blocks of quantum technology.

Researchers and engineers at the University of Sydney and Microsoft Corporation have opened the next chapter in quantum technology with the invention of a single chip that can generate control signals for thousands of qubits, the building blocks of quantum computers.

“To realize the potential in quantum calculation, machines will have to serve thousands, if not millions of qubits, ”said Professor David Reilly, a designer of the chip, who shares a common position with Microsoft and the University of Sydney.

“The world’s largest quantum computers currently operate with only 50 or so qubits,” he said. “This small scale is due in part to the limits of the physical architecture that governs qubits.”

“Our new chip puts an end to these limits.”

The results are published in Natural electronics.

Cryogenic Chip Platform In Situ

The cryogenic chip platform in situ in a dilution refrigerator. The unit can operate at 0.1 Kelvin. Credit: University of Sydney

Most quantum systems require quantum bits or qubits to operate at close temperatures absolutely zero (-273.15 degrees). This is to prevent them from losing their ‘quantum unit’, the nature of matter or light that quantum computers need to perform their specialized calculations.

In order for quantum units to do something useful, they need instructions. This means sending and receiving electronic signals to and from qubits. With the current quantum architecture, it involves a lot of wiring.

“Current machines create a beautiful array of wires to control the signals; they look like an inverted gilded bird’s nest or chandelier. They are beautiful but basically impractical. This means that we can not scale the machines up to perform useful calculations. There is a real input-output bottleneck, ”said Professor Reilly, also a Chief Investigator at the ARC Center for Engineered Quantum Systems (EQUS).

Microsoft Senior Hardware Engineer, Dr. Kushal Das, a co-inventor of the chip, said: “Our device removes all those cables. With only two wires carrying information as input, it can generate control signals for thousands of qubits.

“This alters quantum computation.”

David Reilly

Professor David Reilly from the School of Physics at the University of Sydney holds a joint position with Microsoft Corporation. Credit: University of Sydney

The control chip was developed at Microsoft Quantum Laboratories at the University of Sydney, a unique industry-academic partnership that is changing the way scientists tackle technical challenges.

“Building a quantum computer is perhaps the most challenging engineering task of the 21st century. This can not be achieved by working with a small team in a university laboratory in a single country, but needs the scale offered by a global technology giant like Microsoft. , ”Said Professor Reilly.

“Through our partnership with Microsoft, we have not only proposed a theoretical architecture to overcome the input-output bottleneck, we have built it.

“We have demonstrated this by designing a custom silicon chip and connecting it to a quantum system,” he said. “I’m sure to say that this is the most advanced integrated circuit ever built to operate at deep cryogenic temperatures.”

If realized, quantum computers promise to revolutionize information technology by solving problems beyond the reach of classical computers in such diverse fields as cryptography, medicine, finance, artificial intelligence and logistics.

Power budget

Quantum computers are at a similar stage as classical computers were in the 1940s. Machines like ENIAC, the world’s first electronic computer, required spaces with control systems to achieve any useful function.

It has taken decades to overcome the scientific and technical challenges that now allow billions of transistors to fit into your cell phone.

“Our industry faces perhaps even greater challenges in taking quantum computers beyond the ENIAC stage,” said Professor Reilly.

“We have to construct very complex silicon chips that operate at 0.1 Kelvin,” he said. “It’s an environment that is 30 times colder than deep space.”

Dr. Sebastian Pauka’s doctoral research at the University of Sydney involved much of the work of connecting quantum units to the chip. He said: “Working at such cold temperatures means we have an incredibly low power budget. If we try to put more power into the system, it all overheats.”

To achieve their result, researchers in Sydney and Microsoft built the most advanced integrated circuit to operate at cryogenic temperatures.

“We have done this by constructing a system that works in the immediate vicinity of qubits without disrupting their operations,” Professor Reilly said.

“Current control systems for qubits are removed, so to speak, meters away from the action. They are found mostly at room temperature.

“In our system, we do not have to get away from the cryogenic platform. The chip is right there with qubits. That means lower power and higher speeds. It is a real control system for quantum technology.”

Quantum Machine Full Stack

‘The full stack’ is needed for a useful quantum machine: Professor David Reilly is working with Microsoft researchers globally to realize a fault-tolerant universal quantum computer. The device he invented works at the interface between classical and quantum systems. Credit: Microsoft

Years of engineering work

“Figuring out how to control these devices requires many years of engineering development,” said Professor Reilly. “For this device, we started four years ago when the University of Sydney launched its partnership with Microsoft, which represents the largest single investment in quantum technology in Australia.

“We built lots of models and design libraries to capture the behavior of transistors at deep cryogenic temperatures. Then we had to build devices, get them verified, characterized, and eventually connect them to qubits to see them work in practice.”

The Vice Chancellor and Rector of the University of Sydney, Professor Stephen Garton, said: “The entire university community is proud of Professor Reilly’s success and we look forward to many years of continued partnership with Microsoft.”

Professor Reilly said the field has now fundamentally changed. “It’s not just about ‘here’s my qubit’. It’s about how to build all the layers and all the technology to build a real machine.

“Our partnership with Microsoft allows us to work with academic rigor, with the benefit of seeing our results quickly put into practice.”

The Vice-Chancellor (Research), Professor Duncan Ivison, said: “Our partnership with Microsoft has been about realizing David Reilly’s inspired vision of enabling quantum technology. It’s amazing to see that vision come true.”

Professor Reilly said: “If we had remained exclusively in academia, this chip would never have been built.”

The Australian scientist said he does not stop there.

“We’re just getting started on this new wave of quantum innovation,” he said. “The great thing about the partnership is that we are not just publishing a paper and moving on. We can now move forward with the plan to realize quantum technology on an industrial scale.”

Reference: “A cryogenic CMOS chip for generating control signals for multiple qubits” by SJ Pauka, K. Das, R. Kalra, A. Moini, Y. Yang, M. Trainer, A. Bousquet, C. Cantaloube, N. Dick, GC Gardner, MJ Manfra and DJ Reilly, January 25, 2021, Natural electronics.
DOI: 10.1038 / s41928-020-00528-y

This research was supported by Microsoft Corporation and the Australian Research Council Center of Excellence for Engineered Quantum Systems. We recognize the facilities as well as the scientific and technical assistance from the Research and Prototype Foundry, a nuclear research facility at the University of Sydney and part of the Australian National Fabrication Facility (ANFF).

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