Anthropic Says Claude Mythos 5 Designed Quantum Circuits That Beat Published Designs

Anthropic says Claude Mythos 5 designed quantum circuits that improve on the best published designs, in some cases by an order of magnitude or more. The research, announced October 16, covers eight computational primitives drawn from chemistry, optimization, physics simulation and number theory.

The setup was a closed loop. Claude wrote Python implementations, an automated evaluator checked correctness and scored each by qubits multiplied by gates, and Claude revised with no human input between rounds. On modular inversion for elliptic-curve point addition, it worked 53 hours with minimal prompting, then produced what Anthropic calls the first reversible implementation of divsteps with no stored branch history. It checked the approach in large-scale simulations and formalized it in Lean. One circuit in that family uses 12% more qubits but 17x fewer gates than the smallest previous design. In a Reed–Solomon decoder, gate count fell by a factor of 12 versus Google's previous construction.

Singularity Radar, citing the preprint, says seven of the eight tasks cut both Toffoli gate and qubit counts, while the eighth yielded a new reversible architecture for prime-field modular inversion. It also notes that this is a single preprint with no independent validation or hardware-level verification.

My read: the 12%-more-qubits circuit is a trade-off, not a sweep, and that is the more honest result. The announcement gives full numbers for only a few of the eight tasks. Until someone else reruns the evaluator, this is a strong claim from the company reporting the results.