The quantum computing space seems to deliver new breakthroughs every other week that aim to increase both the usefulness and computing power of quantum-based solutions. As reported by Sky News, the latest development from the University of New South Wales in Sydney, Australia could enable quantum systems that leverage millions of qubits.
We've detailed many quantum computing breakthroughs already: from pre-emptive, quantum-resistant cryptographic algorithms to discoveries of new materials passing through self-contained quantum chips, the quantum computing space has been in an accelerating vector for some time now. And researchers with the University of New South Wales in Sydney, Australia, have just turned the innovation up to eleven, after having seemingly solved the quantum scaling problem. This latest development could enable quantum systems that leverage millions of qubits, instead of the current maximum hovering around one hundred. And to harness millions of qubits seems like quite the important step in increasing the quantum computing market's value in the long term - it's estimated the Quantum Computing as a Service (QCaaS) market will rise up to $26 billion before the end of the decade.
The Sydney researchers approached the quantum scaling problem from the control side of the equation. Whenever there is an automated system that is meant to operate on its own, there has to be a control mechanism that enables the user to change the input variables. Nowadays in quantum computing, this happens via microwave electromagnetic fields - essentially, next to every single qubit, quantum systems feature a wire through which an electrical current is conducted. This, in turn, generates a magnetic field according to the intensity of the current, which enables the quantum computer's user to manipulate the qubit's value and to keep the qubit stable enough so as to perform the actual calculation that's required of it.
This solution features a major problem that was making it more difficult to scale quantum computers, however: heat. Wires conducting electrical currents get hotter the more sustained or more intense that current is; and since the microwave electromagnetic field is one with a small reach, scientists were having to essentially put in a single wire right next to each qubit. You can imagine what the result would be from trying to scale such a design towards millions of the little computational resources in this manner. However, having millions of different wires in the quantum chip's real estate would not only take up too much space, it would also compromise one other current requirement for achieving stability in quantum computing efforts: qubits currently can only provide effective work, and maintain their quantum states, when cooled to sub-zero temperatures around - 270 Celsius. More wires mean higher energy consumption and higher heat output - which means it becomes harder and harder to maintain that target temperature.
The solution was a simple one, really: instead of trying to control each qubit with a single wire, the team tried to design a system that enabled an electromagnetic field to envelop the qubits from above, and that could act upon all of them at the same time. "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," said Dr Pla. A new component, a dielectric resonator, was then added to the setup.
"The dielectric resonator shrinks the wavelength down below one millimetre, so we now have a very efficient conversion of microwave power into the magnetic field that controls the spins of all the qubits," Pla added. "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."
Of course, there are other challenges in scaling quantum computers' basic unit, the qubit. However, control of the system doesn't seem to pose a problem anymore. This is an important step on the road to the actual pervasiveness in quantum computing in our future - which is more fact than fiction at this point in time already. A recent report places the quantum computing as a service market as being valued at $4 billion as early as 2025 - from $1 billion in 2020. That figure could increase 6.5x in just five years - it's expected that same market will be worth $26 billion by 2030. And remember that this is a specific section of quantum computing - providing access to quantum computing running time as a service distribution by the likes of Microsoft's Azure and Amazon Web Services. This doesn't take into account investment and research surrounding this market, which would balloon that $26 billion valuation.