# Quantum engineers improved the silicon chip performance by 100 times setting a new standard

Researchers from the University of New South Wales have broken new ground in quantum computing by demonstrating that 'spin qubits'- qubits where the information is stored in the spin momentum of an electron- can store data for up to two milliseconds, 100 times longer than previous benchmarks in the same quantum processor.

Classical computers work with bits—consisting of ones and zeroes—but a quantum computer uses quantum bits or qubits, which, on top of the ones and zeroes, also has a superposition where it can be a one and a zero at the same time. Because of this, operations on qubits can amount to a large number of computations in parallel.

The time that qubits can be manipulated in increasingly complex calculations is known as 'coherence time.'

"Longer coherence time means you have more time over which your quantum information is stored—which is exactly what you need when doing quantum operations. The coherence time is basically telling you how long you can do all of the operations in whatever algorithm or sequence you want to do before you've lost all the information in your qubits," says Ph.D. student Ms. Amanda Seedhouse, whose work in theoretical quantum computing contributed to the achievement.

In quantum computing, the longer the qubits stay spinning, the better the chance that information can be maintained during calculations. When stopped, the information collapses. Researchers found that, by changing the motion of the qubits and by having them move non-stop, the time that they can retain information can be massively improved.

## Individually controlled Qubits

However, there are challenges to this proof-of-concept achievement. Being able to control millions of qubits with just one antenna was a significant step forward. However, the team needed to work out how to manipulate qubits individually to be used in a working quantum computer.

To achieve that, the team created a qubit protocol called "SMART" – short for "Sinusoidally Modulated, Always Rotating, and Tailored."

Through SMART, researchers manipulated each spin qubit to rock back and forth instead of spinning in circles, like the pendulum of a grandfather clock. Then, if an electric field is applied individually to any qubit – putting it out of resonance – it can be put into a different tempo to its neighbors but still moving at the same rhythm.

"Think of it like two kids on a swing who are pretty much going forward and backward in sync," says Ms. Seedhouse. "If we give one of them a push, we can get them reaching the end of their arc at opposite ends, so one can be a 0 when the other is now a 1," said Ms. Seedhouse

The result is that not only can a qubit be controlled individually (electronically) while under the influence of global control (magnetically), but the coherence time is, as stated earlier, substantially longer and suitable for quantum calculations.

## Next steps

According to the researchers, their protocol leverages a potential path for full-scale quantum computers.

"Our next goal is to show this working with two-qubit calculations after showing our proof-of-concept in our experimental paper with one qubit. Following that, we want to show that we can do this for a handful of qubits as well, to show that the theory is proven in practice," added Ingvild Hansen, the lead researcher on the project.

The research is published in Physical Review A, Physical Review B, and Applied Physics Reviews.