发表机构
RIKEN Pioneering Research Institute; RIKEN Center for Quantum Computing; RMIT University; Cornell University（理化学研究所先驱研究机构; 理化学研究所量子计算中心; 皇家墨尔本理工大学; 康奈尔大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文研究能量约束下量子读取容量，提出基于相对熵的逆界与半定近似可达速率，并证明非自适应协议足以实现联合经典-量子通道的无约束容量。
AI 中文摘要
在量子读取中，经典消息被编码为量子通道序列，并通过探测通道和处理其输出来恢复。我们研究了在探测能量的平均约束下，有限维通道的有限族的读取容量，允许在通道使用之间进行任意自适应操作。利用Belavkin-Staszewski相对熵的输入依赖链式法则，我们推导出一个逆界，表示为涉及通道Choi算子和算子相对熵的优化问题。该表述允许半定近似，并且在无能量约束时简化为通道信息半径。为了获得可达速率，我们构造了标准非自适应读取界的双线性半定下近似。交替优化产生可行的探测态和编码分布，其Holevo信息给出了可直接评估的可达速率。对于联合经典-量子通道，我们基于Umegaki相对熵推导了一个单独的逆界。在无能量约束下，该逆界与非自适应可达速率匹配，恢复了Pascual Abraldes和Winter最近的结果：非自适应协议足以实现联合经典-量子通道的无约束读取容量。
英文摘要
In quantum reading, classical messages are encoded in sequences of quantum channels and recovered by probing the channels and processing their outputs. We study the reading capacity of a finite family of finite-dimensional channels under an average constraint on the probing energy, allowing arbitrary adaptive operations between channel uses. Using an input-dependent chain rule for the Belavkin-Staszewski relative entropy, we derive a converse bound expressed as an optimization involving channel Choi operators and the operator relative entropy. This formulation admits semidefinite approximations and reduces, without an energy constraint, to a channel information radius. To obtain achievable rates, we construct bilinear semidefinite lower approximations to a standard non-adaptive reading bound. Alternating optimization produces feasible probe states and encoding distributions, whose Holevo information gives a directly evaluable achievable rate. For jointly classical-quantum channels, we derive a separate converse based on the Umegaki relative entropy. Without an energy constraint, this converse matches a non-adaptive achievable rate, recovering a recent result of Pascual Abraldes and Winter: non-adaptive protocols suffice to achieve the unconstrained reading capacity of jointly classical-quantum channels.
Comments22+5 pages, 2 figures
