What was found?
French quantum computing firm Alice & Bob has recalculated the quantum resources needed to break RSA-2048 encryption. By its estimate, 23,000 "cat qubits" could be enough, with the cracking process taking about 3.14 days. A larger system could do the same job in 1.5 hours.
RSA-2048 is a foundational encryption standard for digital infrastructure, from banking to e-commerce. Breaking it is considered practically impossible with classical computers.
Why did the number drop so much?
Peter Shor's 1994 algorithm already showed the theoretical path to breaking RSA; what was missing was a quantum computer large and accurate enough to run it. In 2019, Google researchers predicted 20 million physical qubits would be needed. That figure has fallen below one million in six years.
Two forces drive the decline: mathematicians making the algorithm more efficient over 30 years, and improvements in the logical performance of qubits. Alice & Bob's 2023 estimate was 350,000 qubits; with its updated cat-qubit design, the number is now 23,000.
What comes next?
23,000 qubits is not achievable today, but the firm believes it could be possible within a few years and that RSA-2048 would then be obsolete. The main bottleneck is fitting the infrastructure needed to run a system at that scale into a reasonably sized laboratory.
The research notes that post-quantum encryption standards already exist but have not been extensively tested. The authors urge the cybersecurity community to test these algorithms more rigorously and migrate systems before quantum computers become more common. The study has not been peer-reviewed and was published in the Cryptology ePrint Archive.
