【arXiv导读】近期量子计算系统的混合程序设计（Hybrid Programming for Near-term Quantum Computing Systems) [arXiv:1805.09279]

题目：Hybrid Programming for Near-term Quantum Computing Systems

作者：A. J. McCaskey, E. F. Dumitrescu, D. I. Liakh, and T. S. Humble

单位：Quantum Computing Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 37831

摘要：
Recent computations involving quantum processing units (QPUs) have demonstrated a series of challenges inherent to hybrid classical-quantum programming, compilation, execution, and verification and validation. Despite considerable progress, system-level noise, limited low-level instructions sets, remote access models, and an overall lack of portability and classical integration presents near-term programming challenges that must be overcome in order to enable reliable scientific quantum computing and support robust hardware benchmarking. In this work, we draw on our experience in programming QPUs to identify common concerns and challenges, and detail best practices for mitigating these challenge within the current hybrid classical-quantum computing paradigm. Following this discussion, we introduce the XACC quantum compilation and execution framework as a hardware and language agnostic solution that addresses many of these hybrid programming challenges. XACC supports extensible methodologies for managing a variety of programming, compilation, and execution concerns across the increasingly diverse set of QPUs. We use recent nuclear physics simulations to illustrate how the framework mitigates programming, compilation, and execution challenges and manages the complex workflow present in QPU-enhanced scientific applications. Finally, we codify the resulting hybrid scientific computing workflow in order to identify key areas requiring future improvement.

论文内图示：

简评：
美国能源部的下属实验室——橡树岭国家实验室——也紧跟着最近的量子计算热潮。普适量子计算机的制造难度在物理学和计算科学领域内可谓路人皆知。IBM、Microsoft、和Google在这一领域内的投入虽然带来了飞跃性的发展，但也让更多人意识到普适量子计算的难度之大。尽管如此，这一困难似乎并非无法跨越。解决此问题的思路有两种，一是硬件层面创造出更可控更精确的量子处理器（QPU），还有就是软件层面或理论层面如何找到更适合QPU的算法和编译器。这一篇论文走在第二条思路上。

本论文对现有的QPU的架构，即经典量子杂交系统（hybrid classical-quantum computing system），做了详细的介绍（见上第一图）；并在此基础上讨论了这一系统在编程、编译和执行上的特征和其在实际运用中面临的挑战。针对这些问题，作者也提出了一套称为XACC（ eXtreme-scale ACCelerator）的方法来处理经典计算技术在现有受限的量子芯片上的应用（见上第二图）。简单的说，XACC之于QPU相当于于OpenCL或CUDA至于GPU。

这篇文章及相关研究方向的结果，充分预示了量子芯片的发展潜力。物理层面上，量子芯片的研究逐步进入到比拼设计参数和指标的阶段。而运行于这些芯片上的编程语言和控制语言，自然会在接下来几年中呈现出百花齐放的竞争态势。