量子态纯化的测量速度限制
Record Loss Sets a Rare-Trajectory Limit on Quantum Purification
浏览论文内容
中文总结 AI 辅助
研究量子态纯化的测量速度限制，通过状态杂质平方根的泛函推导出三个匹配限制，适用于各维度、策略和效率，给出了速率常数比例，数值及守恒定律等证实了界限并解决相关难题。
中文摘要 AI 辅助
我们推导了关于受监测系统纯化的三个匹配速度限制，适用于任何有限维度、每种策略和效率。这三个限制均由一个泛函设定，即状态杂质的平方根，其最大衰减率是一个与状态无关的常数。对于量子比特，这简化为行列式的平方根，在单位效率下与协议无关的衰减是一个严格的零测试。三个速率常数的比例为二比四比八，且在该平方根（半矩）处达到冻结。数值结果证实了这些界限；对于量子比特，一个守恒定律解决了局部与全局最优性难题，加倍反馈恰好花费最小值的两倍。
英文摘要
Continuous quantum feedback uses time-resolved measurement records to steer monitored systems toward pure states. Yet how the information available to a controller determines the ultimate purification speed remains unresolved. We establish this relation for a qubit under fixed-spectrum Hermitian monitoring with detector loss, obtaining the exact long-time impurity-moment spectrum optimized over causal basis controls at each horizon. Rare records with nearly canceled evidence then make all moments from half order upward decay at the Bhattacharyya information rate between two quantum nondemolition record laws. Aligned quantum nondemolition monitoring preserves that binary distinguishability and attains the limit, while complete detection restores an order-dependent branch. The mechanism extends to higher dimensions, where an attainable rank-two ceiling lies above the full-rank qutrit upper bound over a finite moment interval, establishing retained record distinguishability as a purification resource.
