Distributed quantum applications impose requirements on the quality of the quantum states that they consume. When analyzing architecture implementations of quantum hardware, characterizing this quality forms an important factor in understanding their performance. Fundamental characteristics of quantum hardware lead to inherent tradeoffs between the quality of states and traditional performance metrics such as throughput. Furthermore, any real-world implementation of quantum hardware exhibits time-dependent noise that degrades the quality of quantum states over time. Here, we study the performance of two possible architectures for interfacing a quantum processor with a quantum network. The first corresponds to the current experimental state of the art in which the same device functions both as a processor and a network device. The second corresponds to a future architecture that separates these two functions over two distinct devices. We model these architectures as Markov chains and compare their quality of executing quantum operations and producing entangled quantum states as functions of their memory lifetimes, as well as the time that it takes to perform various operations within each architecture. As an illustrative example, we apply our analysis to architectures based on Nitrogen-Vacancy centers in diamond, where we find that for present-day device parameters one architecture is more suited to computation-heavy applications, and the other for network-heavy ones. Besides the detailed study of these architectures, a novel contribution of our work are several formulas that connect an understanding of waiting time distributions to the decay of quantum quality over time for the most common noise models employed in quantum technologies. This provides a valuable new tool for performance evaluation experts, and its applications extend beyond the two architectures studied in this work.

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关于两种分布式量子架构的量子性能评估

分布式量子应用对它们消耗的量子态的质量提出了要求。在分析量子硬件的架构实现时，表征这种质量是了解其性能的重要因素。量子硬件的基本特性导致状态质量与吞吐量等传统性能指标之间的固有权衡。此外，量子硬件的任何实际实现都表现出与时间相关的噪声，随着时间的推移会降低量子态的质量。在这里，我们研究了用于将量子处理器与量子网络连接的两种可能架构的性能。第一个对应于现有技术的当前实验状态，其中同一设备既用作处理器又用作网络设备。第二个对应于在两个不同设备上分离这两个功能的未来架构。我们将这些架构建模为马尔可夫链，并比较它们执行量子操作和产生纠缠量子态的质量，作为其内存寿命的函数，以及在每个架构中执行各种操作所需的时间。作为一个说明性示例，我们将我们的分析应用于基于钻石中氮空位中心的架构，我们发现对于当今的设备参数，一种架构更适合计算密集型应用程序，而另一种架构则适用于网络密集型应用程序。除了对这些架构的详细研究，我们工作的一个新贡献是几个公式，它们将等待时间分布的理解与量子技术中最常见的噪声模型的量子质量随时间的衰减联系起来。这为性能评估专家提供了一个有价值的新工具，其应用范围超出了这项工作中研究的两种架构。