Bosonic Quantum Communication Beyond the Thermal Threshold
Holevo and Werner's 1999 lower bound on the quantum capacity of the bosonic thermal attenuator comes from thermal inputs. Is it optimal? The paper proves it is exactly the supremum over single-mode Gaussian states, then exhibits a non-Gaussian state that beats it, giving positive quantum capacity in a region where every single-mode Gaussian input yields none.
- Result
- Disproved
- Status
- Resolved
- AI contribution
- AI-discovered
- Method
- Construction
- Field
- Quantum Information, Bosonic Channels
- Posed by
- Alexander Holevo and Reinhard Werner
- Year posed
- 1999
- Years open
- 27y
- Solved
- 2026-07-29
- Model
- ChatGPT 5.6 Sol
- Vendor
- OpenAI
- Collaborators
- Francesco Anna Mele, Giuseppe Catalano, Marco Fanizza, Vittorio Giovannetti, Ludovico Lami
- Verification
- Unreviewed
- Publication
- Preprint
- Significance
- 25 / 100
- Disclosed cost
- —
- Wikipedia
- No dedicated article
What the AI did
From the paper's own AI-assisted research statement: some of the authors had tried hard to find such a non-Gaussian counterexample several years ago and failed; they tried again with ChatGPT 5.5 and failed again; ChatGPT 5.6 Sol then gave them the families of non-Gaussian counterexamples. They call the AI crucial to the work while taking full responsibility for its content.
Verification
No independent review, but stronger than a bare claim: Appendix A turns the numerical evaluation into a rigorous bound by enclosing every quantity in certified real intervals, and a second certified witness is given in Appendix B. Preprint, not refereed.