Speediest quantum operation yet

Australian physicists build a super-fast version of the central building block of a quantum computer.

Australian scientists have linked together two electron spins embedded in a silicon chip to form a two-qubit gate, the fundamental building block of a quantum computer.

The gate is 200 times faster than any other of its type, taking a speedy 0.8 nanoseconds to complete an operation, and uses atom-based qubits that are known for their high accuracy and extremely low noise.

The team from UNSW Sydney reports in the journal Nature that the device is of a type known as a SWAP gate, in which quantum information is exchanged between the two qubits: electron spins attached to phosphorus atoms embedded in the silicon crystal.

The speed of the gate comes from the close proximity of the two atoms, just 13 nanometres apart. At this small separation their interaction can be strong yet still tightly controlled.

Although isolated, they were close enough to be pushed together by a voltage to enable information swapping.

Team leader, and 2018 Australian of the Year, Michelle Simmons says the precision required to make the device was at the limit of what was humanly possible.

“A lot of people thought this would not be possible. To be able to control nature at its very smallest level so that we can create interactions between two qubits but also individually talk to each qubit without disturbing the other is incredible,” she says.

Now the team has created a twoqubit gate, it plans to combine them to start building a fully-fledged quantum computer. Its goal is a 10-qubit integrated circuit, which it aims to create in the next three to four years.