# Intrinsic and Measured Information in Separable Quantum Processes

## TL;DR

This paper explores quantum information properties of separable quantum processes, providing bounds on classical information, methods for source synchronization, and techniques for reconstructing quantum sources with various memory models.

## Contribution

It introduces quantum-information-theoretic bounds, synchronization protocols, and reconstruction methods for separable quantum processes, advancing understanding of their classical and quantum informational structure.

## Key findings

- Bounds on classical information from quantum sources
- Protocols for source synchronization using POVMs
- Methods for reconstructing quantum sources with different memory models

## Abstract

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.