Breaking encryption with a quantum computer just got 10 times easier

The amount of quantum computing power needed to crack a common data encryption technique has been increased tenfold. This makes the encryption method even more vulnerable to quantum computers, which may be able to reach the reduced size within the decade.

The RSA algorithm is one of the most widely used encryption algorithms, used for things like online banking and secure communication. It is based on the mathematical difficulty of finding which two prime numbers were multiplied together to make a very large number. Since the 1990s, researchers have known that this difficulty could be circumvented by using a quantum computer, but the possibility was considered theoretical because the size needed for such a quantum computer was much larger than it could be built.

This has slowly begun to change as researchers built larger quantum computers and the estimated size needed has decreased. In 2019, Craig Gidney at Google Quantum AI co-authored a paper that reduced these requirements from 170 million to 20 million quantum bits, or qubits. And in 2025, Gidney developed a way to cut that number to less than a million qubits. Now Paul Webster at Iceberg Quantum in Australia and his colleagues have managed to further reduce the number to around 100,000 qubits.

The researchers’ study builds on Gidney’s work in terms of algorithmic improvements, but they assume that a different scheme is used to connect and arrange qubits called qLDPC code. In previous schemes, qubits could only interact with their nearest neighbors, but qLDPC code means they can interact with qubits that are further away. This approach increases connectivity and effectively increases the density of information in the quantum computer.

Given this connectivity, the team estimated that for 98,000 superconducting qubits, such as those currently made by IBM and Google, it would take about a month of computing time to break a common form of RSA encryption. To achieve the same in a day would require 471,000 qubits.

Several quantum computing companies aim to build quantum computers with hundreds of thousands of qubits within the decade, and the new estimate is largely agnostic to what they would be made of, depending only on the error rate and the speed of the quantum computer. Putting aside the practicalities of running a calculation for a month, can Iceberg Quantum’s scheme actually be implemented in practice? Anyone in charge of a quantum computer that can do that would have access to many emails, bank accounts or even confidential government files protected with RSA encryption.

“These stricter requirements make the hardware more difficult to make, and making the hardware is already the hardest part,” says Gidney. Similarly, Scott Aaronson of the University of Texas at Austin wrote on his blog that his main reservation with the new estimate is the difficulty of practically constructing the necessary connections between distant qubits.

IBM researchers have been championing qLDPC codes for the past few years, and they have made the firm’s quantum computing hardware more accessible to them, but how successful this approach might be remains unclear. An IBM spokesperson said in a statement that qLDPC codes will be a “cornerstone” of their quantum computers, but did not comment on whether the new scheme could be realized.

Connections between distant qubits are much easier to implement when they are made of extremely cold atoms or ions, two quantum computing approaches that have gained prominence in recent years. But these quantum computers also work more slowly, which, according to the new study, could put the number back into the millions when it comes to breaking RSA encryption.

“I think it’s important to never be conservative with the timelines for things like this happening,” says Lawrence Cohen, also at Iceberg Quantum. “Anyone who breaks RSA will have major consequences, and it’s always much, much better to err on the side of this, and to a large extent sooner rather than later.”

He says that breaking RSA encryption is a well-studied problem and therefore a great benchmark for anyone looking to build a powerful quantum computer, but the team’s approach can also be used to run better and more useful simulations of quantum materials and quantum chemistry.