A Pivotal Breakthrough in Quantum Computing

A radical new technique has been discovered to control millions of spin qubits by Quantum engineers from UNSW Sydney (The University of New South Wales). Dr. Jarryd Pla and his team have made a quantum leap on the road to a full-scale quantum computer, in doing so they have also made the development of near-term silicon quantum processors possible.

Dr Jarryd Pla, a faculty member in UNSW’s School of Electrical Engineering and Telecommunication says his research team has worked tirelessly to solve this decades-old problem, how to control millions of qubits without taking up unnecessary space with excessive wiring, which will use more electricity and more importantly generate more heat? Qubits are the basic qubits of information in a silicone quantum processor.

“Up until this point, controlling electron spin qubits relied on us delivering microwave magnetic fields by putting a current through a wire right beside the qubit,”
“This poses some real challenges if we want to scale up to the millions of qubits that a quantum computer will need to solve globally significant problems, such as the design of new vaccines.”
“First off, the magnetic fields drop off really quickly with distance, so we can only control those qubits closest to the wire. That means we would need to add more and more wires as we brought in more and more qubits, which would take up a lot of real estate on the chip.”

-Dr Pla

Chips must operate below – 270°C, which is made difficult when adding more heat-generating wires because of magnetic field drop off, which is why it was extremely important to find a way to scale up the millions of qubits, without the unwanted heat it generates.

Eureka Moment

Until now, no one has figured out a practical way to control all cubits simultaneously. The solution to the problem is simultaneous manipulation of all the qubits by a magnetic field above the chip.

“First we removed the wire next to the qubits and then came up with a novel way to deliver microwave-frequency magnetic control fields across the entire system. So, in principle, we could deliver control fields to up to four million qubits,”

says Dr. Pla

A Dielectric Resonator is a groundbreaking crystal pyramid introduced by Dr Pla and his team, which sits above the silicon chip. It works by shrinking the wavelength of microwaves directed into the Resonator down to a much smaller size

“The dielectric resonator shrinks the wavelength down below one millimeter, so we now have a very efficient conversion of microwave power into the magnetic field that controls the spins of all the qubits.
“There are two key innovations here. The first is that we don’t have to put in a lot of power to get a strong driving field for the qubits, which crucially means we don’t generate much heat. The second is that the field is very uniform across the chip, so that millions of qubits all experience the same level of control.”

A Dielectric Resonator is a groundbreaking crystal pyramid introduced by Dr Pla and his team. It works by shrinking the wavelength of microwaves directed into the Resonator down below one millimetre. The key innovation this produces is that a lot less heat is produced and the field is very uniform across the chip, causing millions of qubits to all experience the same level of control. Read more: How a simple crystal could help pave the way to full-scale quantum computing

Quantum Team-up

Dr Pla and his team did not have the silicon qubits to test their prototype resonator technology on. So, he spoke to his engineering colleague at UNSW, Scientia Professor Andrew Dzurak, whose team had over the past decade demonstrated the first and the most accurate quantum logic using the same silicon manufacturing technology used to make conventional computer chips.

“I was completely blown away when Jarryd came to me with his new idea,and we immediately got down to work to see how we could integrate it with the qubit chips that my team has developed.”
“We put two of our best PhD students on the project, Ensar Vahapoglu from my team, and James Slack-Smith from Jarryd’s.
“We were overjoyed when the experiment proved successful. This problem of how to control millions of qubits had been worrying me for a long time, since it was a major roadblock to building a full-scale quantum computer.”

-Prof Dzurak

Quantum computers using thousands of qubits to solve problems of commercial significance was once only a dream in the 1980’s but is now approaching within the next decade. Almost improbable solutions can be found to climate change, vaccine and medicine design, code decryption and artificial intelligence through quantum computing.

Looking ahead

Soon the team wants to simplify the design of near-term silicon quantum processors.

“Removing the on-chip control wire frees up space for additional qubits and all of the other electronics required to build a quantum processor. It makes the task of going to the next step of producing devices with some tens of qubits much simpler,”

-Prof Dzurak

In Summary

Dr Pla and his team, in partnering with Professor Andrew Dzurak and his team, has made dramatic advancements in the steps towards a full-scale quantum computer. By creating a revolutionary technique of controlling millions of spin qubits, while creating the possibility of developing near term silicon quantum processors. All without sacrificing overheating or space issues. To read the Full original article feel free to visit ‘Missing jigsaw piece’ Engineers make critical advance quantum computer design.

“While there are engineering challenges to resolve before processors with a million qubits can be made, we are excited by the fact that we now have a way to control them,”

-Dr Pla