(SciTechDaily) Quantum engineers from UNSW Sydney have removed a major obstacle that has stood in the way of quantum computers becoming a reality: they discovered a new technique they say will be capable of controlling millions of spin qubits – the basic units of information in a silicon quantum processor.
With their latest research, the team has found what they consider ‘the missing jigsaw piece’ in the quantum computer architecture that should enable the control of the millions of qubits needed for extraordinarily complex calculations.
Dr. Jarryd Pla, a faculty member in UNSW’s School of Electrical Engineering and Telecommunications says his research team wanted to crack the problem that had stumped quantum computer scientists for decades: how to control not just a few, but millions of qubits without taking up valuable space with more wiring, using more electricity, and generating more heat.
The solution to this problem involved a complete reimagining of the silicon chip structure. Rather than having thousands of control wires on the same thumbnail-sized silicon chip that also needs to contain millions of qubits, the team looked at the feasibility of generating a magnetic field from above the chip that could manipulate all of the qubits simultaneously.
“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.
Dr. Pla and the team introduced a new component directly above the silicon chip – a crystal prism called a dielectric resonator. When microwaves are directed into the resonator, it focuses the wavelength of the microwaves down to a much smaller size.
“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.”