Stationary quantum information sources emit sequences of correlated qudits -- that is, structured quantum stochastic processes. If an observer performs identical measurements on a qudit sequence, the outcomes are a realization of a classical stochastic process. We introduce quantum-information-theoretic properties for separable qudit sequences that serve as bounds on the classical information properties of subsequent measured processes. For sources driven by hidden Markov dynamics we describe how an observer can temporarily or permanently synchronize to the source's internal state using specific positive operator-valued measures or adaptive measurement protocols. We introduce a method for approximating an information source with an independent and identically-distributed, Markov, or larger memory model through tomographic reconstruction. We identify broad classes of separable processes based on their quantum information properties and the complexity of measurements required to synchronize to and accurately reconstruct them.
翻译:静止量子信息源释放相关量子序列, 即结构化量子随机程序。 如果观察者对量子序列进行相同的测量, 其结果将是一个古典随机过程的实现。 我们引入了量子信息理论特性, 以作为随后测量过程传统信息属性的界限的可分离量子序列。 对于由隐藏的 Markov 动态驱动的源, 我们描述观察者如何使用特定的积极操作者估价措施或适应性测量规程, 临时或永久同步到源国的内部状态。 我们引入了一种方法, 以独立和同样分布的、 Markov 或更大的记忆模型来接近信息源, 通过图象重建。 我们根据它们的量子信息属性以及同步和准确重建它们所需的测量的复杂性, 确定广泛的分离过程类别 。</s>