SAN FRANCISCO – Google has claimed a breakthrough in quantum computing research, saying an experimental quantum processor completed in just a few minutes a calculation that would take a traditional supercomputer thousands of years.
The findings, published Wednesday in the scientific journal Nature, show that “quantum speedup is achievable in a real-world system and is not precluded by any hidden physical laws,” the researchers wrote.
Quantum computing is a nascent — and somewhat bewildering — technology for vastly faster information processing. Quantum computers might one day revolutionize tasks that would take existing computers years, including the hunt for new drugs and optimizing urban and transportation planning.
Regular computers, even the fastest, function in binary fashion: They carry out tasks using tiny fragments of data known as bits that are only ever either one or zero.
But fragments of data on a quantum computer, known as qubits, can be both one and zero at the same time. This property, known as superposition, means a quantum computer, made up of several qubits, can crunch an enormous number of potential outcomes simultaneously.
The computer harnesses some of the most mind-boggling aspects of quantum mechanics, including a phenomenon known as “entanglement” — in which two members of a pair of bits can exist in a single state, even if far apart.
Adding extra qubits therefore leads to an exponential boost in processing power.
Big tech companies including Google, Microsoft, IBM and Intel are avidly pursuing the technology.
“Quantum things can be in multiple places at the same time,” said Chris Monroe, a University of Maryland physicist who is also the founder of the quantum startup IonQ. “The rules are very simple — they’re just confounding.”
Google’s findings are already facing pushback from other industry researchers. A version of Google’s paper leaked online last month and researchers caught a glimpse before it was taken down.
IBM quickly took issue with Google’s claim that it had achieved “quantum supremacy,” a term that refers to a point when a quantum computer can perform a calculation that a traditional computer can’t complete within its lifetime. Google’s leaked paper showed that its quantum processor, Sycamore, finished a calculation in three minutes and 20 seconds — and that it would take the world’s fastest supercomputer 10,000 years to do the same thing.
But IBM researchers say that Google underestimated the conventional supercomputer, called Summit, and said it could actually do the calculation in 2.5 days. Summit was developed by IBM and is located at the Oak Ridge National Laboratory in Tennessee.
Google has not commented on IBM’s claims.
Whether or not Google has achieved quantum supremacy may matter to competitors, but the semantics could be less important for the field of quantum research. What it does seem to indicate is that the field is maturing.
“The quantum supremacy milestone allegedly achieved by Google is a pivotal step in the quest for practical quantum computers,” John Preskill, a Caltech professor who originally coined the term “quantum supremacy,” wrote in a column after the paper was leaked.
It means quantum computing research can enter a new stage, he wrote, though a significant effect on society “may still be decades away.”
The calculation employed by Google has little practical use, Preskill wrote, other than to test how well the processor works. Monroe echoed that concern.
“The more interesting milestone will be a useful application,” he said.
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