Breaking encryption with a quantum computer just got 10 times easier

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

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

This slowly began to change as researchers built larger quantum computers and the estimated size needed decreased. In 2019, Craig Gidney of Google Quantum AI co-authored a paper reducing these requirements from 170 million to 20 million quantum bits, or qubits. And in 2025, Gidney has found a way to reduce that number to less than a million qubits. Now, Paul Webster of Iceberg Quantum in Australia and his colleagues have managed to reduce that number further 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 organize the qubits, called qLDPC code. In previous schemes, qubits can only interact with their nearest neighbors, but the qLDPC code means they can interact with qubits further away. This approach increases connectivity and effectively increases the information density within the quantum computer.

Given this connectivity, the team estimated that for 98,000 superconducting qubits, like those currently made by IBM and Google, it would take about a month of computing time to break a common form of RSA encryption. Achieving the same thing 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 independent of the material they would be made from, relying solely on their error rates and the speed of the quantum computer. Putting aside the practicality of performing a calculation for a month, could Iceberg Quantum’s system actually be implemented in practice? Anyone responsible for a quantum computer capable of doing this would have access to numerous emails, bank accounts or even confidential government files protected by RSA encryption.

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

IBM researchers have championed qLDPC codes in recent years and made the company’s quantum computing hardware more sensitive to these codes, but the success of this approach remains uncertain. An IBM spokesperson said in a statement that qLDPC codes would be the “cornerstone” of its quantum computers, but did not say whether the new system 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 operate more slowly, which the new study suggests could bring their numbers down into the millions when it comes to breaking RSA encryption.

“I think it’s important to never be conservative about the timelines for things like this to happen,” says Lawrence Cohen, also at Iceberg Quantum. “Someone breaking the RSA would have serious consequences, and it’s always best to err on the side of excess, as it could very well happen sooner rather than later.”

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