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'Dynamical decoupling' technique improves performance of quantum computers, claims University of Southern California study

Rigetti's 19-qubit Acorn and IBM's 16-qubit QX5 quantum computers used in the study

'Dynamical decoupling' technique improves performance of quantum computers, claims University of Southern California study
An 8-qubit quantum processor which powers a small quantum computer. Image by Rigetti Computin
  • Dev Kundaliya
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Scientists at the University of Southern California (USC) have come up with an innovative approach to boost the performance of quantum computers. The technique, called dynamical decoupling (DD), increases the fidelity of results by suppressing erroneous calculations during computation - an essential step to boost the performance of quantum computers.

"This is a step forward," said Daniel Lidar, director of the USC Centre for Quantum Information Science and Technology.

"Without error suppression, there's no way quantum computing can overtake classical computing."

Quantum computers work in a fundamentally different way than classical computers. Quantum computers use qubits (or quantum bits) as the basic building blocks of computing.

Today's quantum computers contain only a few qubits as any attempt to add more qubits makes them prone to environmental noise, which eventually disturbs the computing process and results in erroneous calculations. USC scientists claim that their latest study addresses this weakness of quantum computers, which hinders them to perform up to their actual potential.

In the study, Rigetti Computing and IBM provided the researchers cloud access to their small-scale, general-purpose quantum computers: Rigetti's 19-qubit Acorn and IBM's 16-qubit QX5, respectively.

To achieve dynamic decoupling in their experiments, researchers used timed pulses of small amounts of electromagnetic energy and focused them on superconducting qubits. By using the pulses in a controlled way, they were able to enclose the qubits in a microenvironment, which was sequestered from surrounding ambient noise. The technique enabled researchers to perpetuate a quantum state in their computers.

"We tried a simple mechanism to reduce error in the machines that turned out to be effective," said Bibek Pokharel, a doctoral student at USC and the first author of the study.

In these experiments, the time sequences were exceptionally small with up to 200 pulses spanning up to 600 nanoseconds.

The results were encouraging for the team. The final fidelity for the IBM quantum computer improved from 28.9 per cent to 88.4 per cent. For the Rigetti Acorn quantum computer, final fidelity improved from 59.8 per cent to 77.1 per cent.

The findings also showed that more pulses always enhanced fidelity results for the Rigetti computer. However, for IBM computer, there was a maximum limit of about 100 pulses.

Overall, the dynamical decoupling technique demonstrated better results than any other quantum error correction method.

The findings of the study are published in journal Physical Review Letters.

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