Measuring the power of a quantum computer just got faster and more accurate


Sandia National Laboratories has designed a faster, more accurate style of testing for quantum computers, like the one shown here. Credit: Bret Latter, Sandia National Laboratories

What does a quantum computer have in common with a premier choice in sports? Both have attracted a lot of attention from talent scouts. Quantum computers, experimental machines capable of performing certain tasks faster than supercomputers, are constantly being evaluated, as are young athletes, for their potential to one day become revolutionary technology.

Now, scout scientists have their first tool to rank a potential technology’s ability to perform realistic tasks, revealing its true potential and limits.

A new type of benchmark test, designed by Sandia National Laboratories, predicts the likelihood that a quantum processor will run a specific program without error.

The so-called mirror circuit method, published today in Physics of nature, is faster and more accurate than conventional tests, helping scientists develop the technologies most likely to lead to the world’s first practical quantum computer, which could dramatically accelerate research in medicine, chemistry, physics, agriculture and national security .

Until now, scientists have measured performance on random operations obstacle courses.

But according to the new research, conventional benchmark tests underestimate many quantum computational errors. This can lead to unrealistic expectations about the power or usefulness of a quantum machine. Mirror circuits offer a more precise test method, according to the document.

A mirror circuit is a computer routine that performs a set of calculations and then the other way around.

“It is a common practice in the quantum computing community to only use random and disordered programs to measure performance, and our results show that this is not the right thing to do,” said the computer scientist Timothy Proctor, a member of Sandia’s Quantum Performance Laboratory who participated in the research.

The new test method also saves time, which will help researchers evaluate increasingly sophisticated machines. Most benchmark tests check for errors by running the same set of instructions on a quantum machine and a conventional computer. If there are no errors, the results should match.

However, because quantum computers perform some calculations much faster than conventional computers, researchers can wait a long time for the end of normal computers.

With a mirror circuit, however, the output should always be the same as the input or an intentional change. So instead of waiting, scientists can immediately check the result of the quantum computer.

New method reveals flaws in conventional performance reviews

Proctor and his colleagues have found that randomized tests miss or underestimate the compound effects of errors. When an error is compounded, it gets worse as the program executes, like a wide receiver taking the wrong path, further and further away from where they are supposed to be at. as the game continues.

By mimicking functional programs, Sandia found that the end results often had larger deviations than randomized tests showed.

“Our benchmarking experiments revealed that the performance of current quantum computers is much more variable on structured programs” than previously known, said Proctor.

The mirror circuit method also gives scientists a better understanding of how to improve current quantum computers.

“By applying our method to today’s quantum computers, we were able to learn a lot about the errors that these particular devices experience, as different types of errors affect different programs in different ways,” said Proctor. “This is the first time that these effects have been observed in multi-qubit processors. Our method is the first tool to probe these large-scale error effects.”

A breakthrough in error mitigation for quantum computers

More information:
Timothy Proctor, Measuring the Capabilities of Quantum Computers, Physics of nature (2021). DOI: 10.1038 / s41567-021-01409-7.

Provided by Sandia National Laboratories

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