Science & Tech · Cybersecurity · 3 hrs ago
Study Estimates Cat-Qubit Computer Could Break RSA-2048 in 3 Days
Researchers at Paris-based Alice & Bob estimate that a quantum computer using 22,593 cat qubits could break an RSA-2048 encryption key in about 3.14 days.
RSA encryption helps protect online activities such as banking, software updates and social media.
The team’s estimate uses Shor’s algorithm, a method designed to use quantum computing to factor large numbers and undermine RSA encryption.
The study is a preprint and has not yet undergone peer review, and its estimates rely on particular assumptions about errors and error correction.
The estimate is far below earlier qubit counts, though it does not show that a machine capable of breaking RSA-2048 has been built.
The researchers also estimate that linking 10 quantum computers could reduce the task to about 1.25 hours, using 610,530 cat qubits.
A preprint study estimates that 22,593 superconducting cat qubits could factor an RSA-2048 key in 3.14 days.
The study was led by researchers from Paris-based quantum computing firm Alice & Bob and has not yet undergone peer review.
The researchers also estimate that linking 10 quantum computers, with 610,530 cat qubits in total, could do the task in 1.25 hours.
The estimates use Shor’s algorithm, which was designed to speed up the factorization that could break RSA encryption.
The article says the estimates depend on the study’s assumptions about error rates and error correction.
- Who
- A team led by researchers from Alice & Bob, a quantum computing firm headquartered in Paris.
- What
- The team estimated the resources needed for a cat-qubit quantum computer to factor an RSA-2048 key. It estimated 22,593 qubits and 3.14 days.
- When
- The preprint was published on the Cryptology ePrint Archive; ScienceAlert published its article on 2026-11-05.
- Where
- The preprint was posted on the Cryptology ePrint Archive. Alice & Bob is headquartered in Paris.
- Why
- To estimate the resources Shor’s algorithm would need to factor an RSA-2048 key and assess the potential threat to RSA encryption.
This story does not have two clearly opposing sides.
Mathematician Peter Shor designed the algorithm that bears his name.
A resource estimate for Shor’s algorithm was 20 million qubits, according to the researchers’ account.
Alice & Bob’s estimate was 350,000 cat qubits.
Estimates had fallen below one million qubits, according to the article.
ScienceAlert published its report on the Alice & Bob preprint.
- Estimated cat qubits
- 22,593
- Estimated runtime
- 3.14 days to factor an RSA-2048 key
- Linked-machine scenario
- 10 quantum computers with 610,530 cat qubits
- Linked-machine runtime
- 1.25 hours
- Study status
- Preprint; not yet peer reviewed
What people are saying
To our knowledge, no published architecture is smaller at this runtime, which puts us at the frontier of size and speed together
You can trade one for the other, but push too far either way and you end up with a machine that is too big to build, or too slow to matter