June 17, 2021 — Quantum computers could outperform classical computers at many tasks, but only if the errors that are an inevitable part of comp

Correlated Errors in Quantum Computers Emphasize Need for Design Changes

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2021-06-17 19:00:08

June 17, 2021 — Quantum computers could outperform classical computers at many tasks, but only if the errors that are an inevitable part of computational tasks are isolated rather than widespread events.

Now, researchers at the University of Wisconsin–Madison have found evidence that errors are correlated across an entire superconducting quantum computing chip — highlighting a problem that must be acknowledged and addressed in the quest for fault-tolerant quantum computers.

The researchers report their findings in a study published June 16 in the journal Nature. Importantly, their work also points to mitigation strategies.

“I think people have been approaching the problem of error correction in an overly optimistic way, blindly making the assumption that errors are not correlated,” says UW–Madison physics Professor Robert McDermott, senior author of the study. “Our experiments show absolutely that errors are correlated, but as we identify problems and develop a deep physical understanding, we’re going to find ways to work around them.”

The bits in a classical computer can either be a 1 or a 0, but the qubits in a quantum computer can be 1, 0, or an arbitrary mixture — a superposition — of 1 and 0. Classical bits, then, can only make bit flip errors, such as when a 1 flips to 0. Qubits, however, can make two types of error: bit flips or phase flips, where a quantum superposition state changes.