Brandão's generalised quantum Stein's lemma

About 4 years old · traced to

Let (Mn)n(\mathcal{M}_n)_n be a family of sets of quantum states satisfying Axioms 1--5 in Section~, and let DM∞(ρ)D^\infty_{\mathcal{M}}(\rho) denote the corresponding regularised relative entropy. Brandão's generalised quantum Stein's lemma. For every quantum state ρ\rho,

lim⁡ϵ→0lim⁡n→∞1nmin⁡σn∈MnDHϵ(ρ⊗n∥σn)=DM∞(ρ).\lim_{\epsilon \to 0} \lim_{n \to \infty} \frac{1}{n} \min_{\sigma_n \in \mathcal{M}_n} D^\epsilon_H\left(\rho^{\otimes n} \middle\| \sigma_n\right)=D^\infty_{\mathcal{M}}(\rho).

This extends quantum Stein's lemma from a single i.i.d. alternative state to composite hypothesis testing against families of states, and connects the asymptotic hypothesis-testing exponent with the regularised relative entropy. The supplied text presents it as the seminal result of Brandão and does not provide evidence resolving the candidate's status.

References

Primary source

Mario Berta, Fernando G. S. L. Brandão, Gilad Gour, Ludovico Lami, Martin B. Plenio, Bartosz Regula and Marco Tomamichel, “On a gap in the proof of the generalised quantum Stein's lemma and its consequences for the reversibility of quantum resources”, arXiv:2205.02813 (2025).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.