Anthropic says Claude Mythos 5 beat published quantum circuit designs

Anthropic reported that Claude Mythos 5, working in a closed loop with an automated evaluator, designed quantum circuits that outperform the best published designs across eight computational primitives, in some cases by an order of magnitude. The work was led by Andi Gu under Anthropic's STEM Fellows Program with Harvard and QuEra collaborators; a 46-page paper was submitted to arXiv on October 15, 2026.

• In 7 of 8 tasks the circuits cut both Toffoli and qubit counts
• The eighth task produced a new reversible prime-field modular inversion
• Claude worked 53 hours with minimal human input on point addition
• One design uses 12% more qubits but 17x fewer gates