Are today’s rudimentary quantum computers already on the verge of significant achievements unattainable for traditional computers? Or have their capabilities been exaggerated as the practical utility of the technology moves into the future?
These questions have been highlighted in recent days by a group of Chinese researchers claiming to have found a way to crack the RSA encryption that underlies much of today’s online communications.
The likelihood that quantum computers would be able to crack online encryption was widely seen as a danger that could be a decade or more in the future. However, the 24 researchers from a number of China’s top universities and government-backed laboratories said their research showed it could be possible with the quantum technology already available.
The quantum bits or qubits used in today’s machines are very unstable and only hold their quantum states for extremely short periods of time, creating “noise”. As a result, “errors accumulate in the computer and after about 100 operations there are so many errors that the calculation fails,” said Steve Brierley, CEO of quantum software company Riverlane.
This has led to a search for more stable qubits, as well as error-correction techniques to overcome the “noise,” pushing back the date when quantum computers are likely to reach their full potential by many years.
In contrast, the Chinese claim appeared to be an endorsement of today’s “noisy” systems, while at the same time unleashing a wave of concern in the cybersecurity world about a potentially imminent threat to online security.
By the end of last week, a number of researchers at the intersection of advanced mathematics and quantum mechanics had thrown cold water at the claim.
Riverlane’s Brierley said it “may not work” because the Chinese researchers had assumed that a quantum computer could simply run a large number of calculations simultaneously, rather than trying to gain an advantage by applying the system’s quantum properties.
Peter Shor, the American mathematician who first proposed a way for quantum computers to crack encryption, predicted that the inability to do all the calculations at once would mean it would take “millions of years” for a quantum computer to break the performs the calculation proposed in the paper.
The Chinese research comes at a time when many companies working on the technology are racing to prove that today’s “noisy” systems can achieve the so-called quantum advantage — the point at which a quantum computer can perform a useful task more efficiently than a traditional or “classic” machine that initiates the commercial exploitation of the technology.
Four years ago, John Preskill, Professor of Theoretical Physics at the California Institute of Technology, predicted that once quantum systems reached 50-100 qubits in size, they would start to outperform and could be exploited commercially. But that moment has come and gone without quantum systems showing clear superiority. IBM unveiled a 127-qubit computer more than a year ago and announced last month that a new 433-qubit processor will be available in the first quarter of 2023.
These days Preskill sounds more cautious. “My guess is that we’ll have to wait for error-corrected, fault-tolerant quantum computers for practical applications with significant business value,” he said, adding that it’s likely “a long way off.” But he added that today’s systems already have scientific value.
One reason hopes have dwindled is that new ways have been found to program classic computers to do tasks that were thought impossible.
This has pushed the quantum frontier and delayed the moment when people building quantum systems can claim an advantage, said Oskar Painter, head of quantum hardware in the cloud computing division at Amazon, one of the tech companies building its own quantum computer. “You could never finally say, ‘This is going to get better,'” he said.
After years of rising expectations, the lack of practical use for the technology has led some experts to warn of a possible “quantum winter” – a time when disappointment with a new technology leads to a waning interest for a few years. The term is borrowed from the AI “winters” of the 1970s and 1980s, when a number of promising research avenues turned into dead ends and set the field back for a long time.
“People are worried it’s going to be really tough,” said Amazon Web Services’ Painter. However, like many in the field, he said that a short-term backlash is unlikely to affect long-term research funding. “I don’t think it’s going to go away,” he added.
Dwindling hopes of early quantum computing benefits have already helped send shares of a handful of companies that have been riding the industry’s enthusiasm to go public since mid-2021, plummeted.
Based on their peak prices shortly after their IPO, Arquit, IonQ, D-Wave, and Rigetti totaled $12.5 billion. That has since fallen to $1.4 billion. Among the events that have struck quantum companies over the past year, IonQ was hit by a short seller’s report claiming its technology didn’t live up to its claims, while Rigetti founder Chad Rigetti was ousted as CEO before he founded the company left at the end of the year.
Part of the problem the sector is facing has been excessive “hype” around the technology, said Constantin Gonciulea, Wells Fargo’s CTO of advanced technology. He compared the building of expectations regarding quantum to the crypto industry as many non-experts have been drawn into the field and promises for the technology have far exceeded its potential in the near future.
Despite this, companies working on the first quantum machines and software still insist that practical application of the technology is just around the corner – while continuing to carefully avoid making over-precise predictions about exactly when that will be.
David Rivas, Rigetti’s head of engineering and product, said the company still believes it would gain a quantum advantage if its computers had “a few hundred to a few thousand qubits.” Even if they don’t match the performance of today’s supercomputers, they will still be useful if they cost much less or can work faster or more precisely, he said.
For some quantum companies, the startling Chinese claim about online encryption was a sign that the tech’s big moment is near. But for the doubters, the apparent impracticability of the research will serve as confirmation that quantum computing is still more of an impressive scientific experiment than a practical technology.
https://www.ft.com/content/d64e45b4-692a-429e-bc64-146303ec7fdf The hype surrounding quantum computing is declining due to a lack of practical applications