2026-09-28 · arXiv Quantum Physics
arXiv:2609.31221v1 Announce Type: new
Abstract: Different measurements of the same environment can preserve the average quantum channel yet change the feedback strength needed to prepare a state ensemble. We establish this distinction for a multiqubit register under complete Pauli monitoring, targeting the uniform ensemble of real-amplitude pure states. With unit detection efficiency, public records, and bounded Hamiltonian feedback, fixed transverse noise requires a minimum peak strength proportional to $\epsilon^{-1}$ at distributional error $\epsilon$. Tangent noise instead admits a construction requiring only $O[\sqrt{\log(1/\epsilon)}]$. At fixed preparation time, we determine the optimum over all allowed feedback policies and derive a geometric lower bound beyond radial symmetry. The separation identifies the measurement realization as part of the control-resource specification for monitored ensemble preparation.
原文链接：https://arxiv.org/abs/2609.31221
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