Errors are the fundamental barrier to the development of quantum systems. Quantum networks are complex systems formed by the interconnection of multiple components and suffer from error accumulation. Characterizing errors introduced by quantum network components becomes a fundamental task to overcome their depleting effects in quantum communication. Quantum Network Tomography (QNT) addresses end-to-end characterization of link errors in quantum networks. It is a tool for building error-aware applications, network management, and system validation. We provide an overview of QNT and its initial results for characterizing quantum star networks. We apply a previously defined QNT protocol for estimating bit-flip channels to estimate depolarizing channels. We analyze the performance of our estimators numerically by assessing the Quantum Cramèr-Rao Bound (QCRB) and the Mean Square Error (MSE) in the finite sample regime. Finally, we provide a discussion on current challenges in the field of QNT and elicit exciting research directions for future investigation.

中文翻译：

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量子网络断层扫描


错误是量子系统发展的根本障碍。量子网络是由多个组件互连形成的复杂系统，并且会遭受错误累积。表征量子网络组件引入的错误成为克服量子通信中的消耗效应的一项基本任务。量子网络断层扫描 (QNT) 可解决量子网络中链路错误的端到端表征问题。它是用于构建错误感知应用程序、网络管理和系统验证的工具。我们概述了 QNT 及其用于表征量子星网络的初步结果。我们应用先前定义的 QNT 协议来估计位翻转通道来估计去极化通道。我们通过评估有限样本范围内的量子 Cramèr-Rao 界 (QCRB) 和均方误差 (MSE) 来对估计器的性能进行数值分析。最后，我们讨论了 QNT 领域当前的挑战，并为未来的研究提出了令人兴奋的研究方向。