The experimental realization of quantum information systems will be difficult due to how sensitive quantum information is to noise. Overcoming this sensitivity is central to designing quantum networks capable of transmitting quantum information reliably over large distances. Moreover, the ability to characterize communication noise in quantum networks is crucial in developing network protocols capable of overcoming the effects of noise in quantum networks. In this context, quantum network tomography refers to the characterization of channel noise in a quantum network through end-to-end measurements. In this work, we propose network tomography protocols for quantum star networks formed by quantum channels characterized by a single, non-trivial Pauli operator. Our results further the end-to-end characterization of quantum bit-flip star networks by introducing tomography protocols where state distribution and measurements are designed separately. We build upon previously proposed quantum network tomography protocols, as well as provide novel methods for the unique characterization of bit-flip probabilities in stars. We introduce a theoretical benchmark based on the Quantum Fisher Information matrix to compare the efficiency of quantum network protocols. We apply our techniques to the protocols proposed, and provide an initial analysis on the potential benefits of entanglement for Quantum Network Tomography. Furthermore, we simulate the proposed protocols using NetSquid to assess the convergence properties of the estimators obtained for particular parameter regimes. Our findings show that the efficiency of protocols depend on parameter values and motivate the search for adaptive quantum network tomography protocols.

翻译：量子信息系统对噪声的高度敏感性使其实验实现面临挑战。克服这一敏感度是实现远距离可靠传输量子信息的量子网络设计核心。此外，表征量子网络通信噪声的能力对于开发能克服网络噪声效应的协议至关重要。在此背景下，量子网络层析成像指通过端到端测量来表征量子网络中的信道噪声。本研究针对由单一非平凡泡利算子表征的量子信道构成的量子星型网络，提出了相应的网络层析成像协议。通过引入状态分布与测量可独立设计的层析协议，我们推进了量子比特翻转星型网络的端到端表征研究。在已有量子网络层析成像协议的基础上，我们提出了星型网络中比特翻转概率唯一表征的新方法。基于量子Fisher信息矩阵建立了理论基准以比较量子网络协议的效率，并将该技术应用于所提协议，初步分析了纠缠对量子网络层析成像的潜在益处。此外，利用NetSquid仿真所提协议，评估了特定参数条件下估计量的收敛特性。研究结果表明，协议效率依赖于参数取值，这为探索自适应量子网络层析成像协议提供了动机。