Quantum computers are already here, even though it’s not readily apparent. Now, researchers say quantum advantage—the field’s long-promised milestone of outperforming classical computers—appears to have finally arrived. But the story comes with an important caveat.
Research by scientists at the University of Texas at Austin and Colorado computing firm Quantinuum devised and carried out an experiment that demonstrates “unconditional” quantum advantage, sometimes referred to as quantum supremacy. As the researchers phrased it, their “result is provable and permanent: no future development in classical algorithms can close this gap.” The preprint, which has yet to be peer reviewed, was made available on arXiv earlier this month.
Gizmodo reached out to several experts in the field, who affirmed the new results. They added that the experiment, while commendable, isn’t the most practical use of a quantum computer—which already gets flak for its uselessness to everyday users.
Then again, “quantum advantage” is a weird, surprisingly malleable concept with many possible applications. Overall, the results are definitely worth a closer look.
Alice and Bob make a cameo
Quantum enthusiasts may be familiar with Alice and Bob, two fictional characters often summoned for quantum thought experiments. In the context of the new experiment, Alice and Bob are two researchers collaborating on a computation using a single device. They receive different inputs at different points in time, but only Alice can send Bob a message, and not the other way around. Based on Alice’s message, Bob must decide how to measure and interpret to produce a final output.
According to the paper, “the use of a quantum message can provably reduce the amount of communication required by an exponential factor compared to any protocol that uses classical communication alone.” In other words, a small quantum message can replace a much larger classical one. To prove their point, the team repeated the experiment 10,000 times on Quantinuum’s H1-1 trapped-ion quantum computers, coupled with a careful mathematical validation of their protocol.
Surprisingly, they found that a quantum computer only needed 12 qubits (qubits are the smallest unit of information for quantum computers) to solve this problem. By contrast, even the most efficient classical computers needed 330 bits.
A different way to play the game
“This is a very different type of quantum advantage than we have seen before—not better or worse, but it’s just proving something completely different from past experiments,” Bill Fefferman, a computer scientist at the University of Chicago, told Gizmodo in an email. Fefferman previously collaborated with senior author Scott Aaronson but wasn’t involved in the new study.
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