New quantum computer with ‘flip-flop qubits’ hailed as major breakthrough

6 Sep 2017

Abstract illustration of a quantum computer in action. Image: plotplot/Shutterstock

A team of engineers has unveiled a radical new quantum computer design that promises to make quantum chip manufacturing drastically cheaper.

Only a select few major tech corporations and research groups have access to a number of powerful quantum computers, but a team from Australia’s University of New South Wales (UNSW) believes it has found a way to make it a much more affordable pursuit.

In a paper published to Nature Communications, the team of engineers led by Andrea Morello explained that the breakthrough was achieved using its new chip based on ‘flip-flop qubits’.

Unlike a more typical model, the new silicon quantum processor can be scaled up without the precise placement of atoms required in other approaches.

This allows the qubits – a bit of information that can be either a one, zero or both in binary terms – to be placed hundreds of nanometres apart and still remain coupled.

Sitting at the sweet spot

One of the expected challenges of trying to make bigger and bigger supercomputers was that traditional spin-based silicon qubits need to be spaced at a distance of between 10 or 50 nanometres apart.

Proving to be a fine balance, if the atoms were too close or too far apart, the entanglement between qubits – which creates its incredible computing power – is made useless.

So, when computer scientists attempt to create an array of thousands or millions of qubits so close together under the current model, all the control mechanisms also have to be fabricated at the nanometric scale, making it incredibly difficult.

“Our new silicon-based approach sits right at the sweet spot,” said Morello. “It’s easier to fabricate than atomic-scale devices, but still allows us to place a million qubits on a square millimetre.”

Explaining the technology

But perhaps even more impressive is that the new processor contains the flip-flop qubit, an entirely new type of qubit that uses both the nucleus and the electron of an atom.

This means that a qubit ‘zero’ state is defined when the spin of the electron is down and the nucleus spin is up, while the ‘one’ state is when the electron spin is up and the nuclear spin is down.

The study’s lead author, Guilherme Tosi, explained that this allows the atoms to work at greater distances.

“To operate this qubit, you need to pull the electron a little bit away from the nucleus, using the electrodes at the top. By doing so, you also create an electric dipole,” he said.

Morello described this as the crux of the new quantum computer chip. “This means we can now place the single-atom qubits much further apart than previously thought possible,” he said.

“So there is plenty of space to intersperse the key classical components, such as interconnects, control electrodes and readout devices, while retaining the precise atom-like nature of the quantum bit.”

Morello’s team has struck an A$83m deal between UNSW, telco giant Telstra, Australia’s Commonwealth Bank, and the Australian and New South Wales governments to develop, by 2022, a 10-qubit prototype silicon quantum integrated circuit to build the world’s first quantum computer in silicon.

Colm Gorey was a senior journalist with Silicon Republic