Efficient pinning algorithms at the universal separability threshold

Determine whether the pinning procedures of Bakshi, Liu, Moitra, and Tang and of Putterman, Zlokapa, and Cotler provide efficient algorithms for Gibbs-state preparation up to the exact universal separability threshold z_Δ for bounded-degree Pauli Hamiltonians.

Background

The paper develops an efficient approximate sampler only at temperatures separated by a fixed relative margin below z_Δ. Its polymer-based sampler therefore does not establish efficient preparation exactly up to the threshold. The discussion compares this limitation with earlier successive-pinning methods and explicitly leaves open whether those methods can achieve efficient sampling throughout the full regime βJ ≤ z_Δ.

References

Our sampler does not by itself extend the temperature guarantees of the earlier pinning procedures, and it is unclear if the pinning procedures give efficient algorithms up to the threshold $z_\Delta$.

— Sharp universal death of entanglement threshold for Pauli Hamiltonians  (2609.30149 - Kiani, 24 Sep 2026) in Section Discussion

Several open questions remain. The sharpness construction allows the locality of a term to grow with $\Delta$, so the optimal constants at a fixed locality are undetermined (e.g. say $k=2$ local Hamiltonians).

— Sharp universal death of entanglement threshold for Pauli Hamiltonians  (2609.30149 - Kiani, 24 Sep 2026) in Section Discussion

Several open questions remain. The sharpness construction allows the locality of a term to grow with $\Delta$, so the optimal constants at a fixed locality are undetermined (e.g. say $k=2$ local Hamiltonians). One can also ask for thermal thresholds relative to larger classes than product states, such as convex mixtures of states prepared by shallow circuits or circuits in a fixed level of the magic hierarchy. Finally, random Hamiltonians may have typical thresholds different from the worst-case bound.

— Sharp universal death of entanglement threshold for Pauli Hamiltonians  (2609.30149 - Kiani, 24 Sep 2026) in Section Discussion