Atom-based computers could require a fraction of previously estimated qubits
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Powerful quantum computers could be closer than scientists thought.
To unlock the full power of technology, scientists have long believed that quantum computers with millions of quantum bits, or qubits, would be needed. But researchers report that the promise of quantum computers could emerge with just 10,000 qubits.
One of the key tasks that future quantum computers are expected to excel at is cracking the encryption used to secure communications over the Internet. Now scientists have calculated that a widely used type of encryption called elliptic curve cryptography could be thwarted with a quantum computer with 9,988 qubits – although it would take around 1,000 days to crack it.
With approximately 26,000 qubits, encryption could be broken in a dayreport the researchers in an article submitted March 30 to arXiv.org. Another popular form of encryption, RSA-2048, would require 100,000 qubits and 10 days to break, according to researchers at Caltech and quantum computing company Oratomic of Pasadena, Calif.
The calculation suggests that quantum computers could also soon contribute to other areas where machines are expected to have an impact, such as AI, chemistry and materials science.
This new result follows a paper published on arXiv.org in February, in which researchers at Iceberg Quantum in Sydney calculated that RSA encryption could be defeated in a week with a quantum computer of around 100,000 qubits. Both papers, which have not yet been peer-reviewed, suggest a dramatic decrease from the 20 million qubits which was thought necessary only a few years ago.
This decline is largely due to improvements in quantum error correction, the technique by which faulty quantum bits are transformed into reliable computing tools. “This has huge implications for quantum computing,” says physicist Jens Eisert of Freie Universität Berlin, who was not involved in the research. “This work is encouraging [in] that this tells us that it might be more achievable than we think.
A change in atmosphere is taking place following these and other results. “There’s a new wave of hope that quantum computers can really work, and maybe in the next five to 10 years they can actually crack our encryption,” says mathematician Jens Niklas Eberhardt of the Johannes Gutenberg University of Mainz in Germany, who was not involved in the research. “It’s quite astonishing but also terrifying.” The advance could expose secret data and threaten the security of cryptocurrencies such as Bitcoin, which relies on elliptic curve cryptography.
Both papers exploit advanced types of quantum error correction, called low-density quantum parity check codes. Error correction typically works by combining multiple faulty qubits into a reliable logical qubit. These logical qubits are then used to perform calculations. Depending on the number of qubits going into an error-corrected logical qubit, the technique can require a massive qubit overload.
Low-density quantum parity check codes can create logical qubits more efficiently than standard schemes. But they generally require that each qubit be able to interact directly with many other qubits. That’s not easy for many of the larger types of quantum computers, which write their qubits on chips on which the qubits primarily interface with their nearest neighbors.
Oratomic’s work relies on a type of quantum computer with qubits made of individual atoms. Lasers can move atoms, allowing all the qubits to connect with each other. The work suggests that error-correcting quantum computers seem inevitable, says physicist Dolev Bluvstein of Oratomic. “It seems so close and so achievable that there is no way humanity can stop.”
But giving a figure as a reference is only one step. “This doesn’t mean the problem is solved; the fun is just beginning,” says Eisert. Fun by a physicist’s definition, anyway: “There are a lot of details to work out. »
And progress in error correction is coming at a rapid pace. On March 30, researchers at Google Quantum AI published a paper and blog on the company’s website, suggesting that a quantum computer with 500,000 physical qubits running for a few minutes could endanger the security of cryptocurrency.
Overall, the findings prompt scientists to sound the alarm: Internet security should be updated as soon as possible. “This is certainly an even stronger push for people to move to quantum-resistance cryptography now,” computer scientist Scott Aaronson of the University of Texas at Austin said in an email. “They should really get going!”