Semiclassical Approach to Classical Simulation of Quantum Annealers

量子力学支配着微观世界的行为，它的规则与日常生活中最熟悉的物理定律非常不同。21世纪世纪的一个科学挑战是利用量子力学的独特特性来开发新技术。例如，与熟悉的经典计算机相比，基于量子逻辑工作的计算机将提供速度提升和其他优势，至少对于一些几乎难以处理的计算问题。另一种称为量子退火机的机器可以用来解决优化问题。虽然不是一台成熟的量子计算机，但量子退火机在其操作过程中使用了隧道和纠缠，其相对于传统机器的优势是当前许多研究的主题。该项目将试图表明，当前量子退火机中存在的限制意味着这些机器还没有足够的量子力学来提供比传统计算方法更基本的计算优势。如果成功的话，这项工作将清楚地表明，建议修改目前的退火炉，这是技术上可行的，是必要的，这些设备提供有用的改进，传统的计算方法。如果这一说法没有得到证实，这项工作可能会提供洞察力，当当前的量子退火可以预期优于传统的计算机。量子计算承诺优于经典计算的某些问题。然而，建造大规模量子计算机的实验障碍是巨大的。量子退火是一种获得量子优势的中间方法，在过去的十年中，它已经在相当大的规模上实现了。量子退火器解决了优化问题，并且在其操作过程中有实验证据表明量子效应，如隧道和纠缠。关于这些机器何时提供量子优势的一般理论尚不存在，但由于实际硬件的存在，关于它们的操作的大量经验知识正在积累。这项工作将解决他们是否可以提供一个独特的量子优势超过经典的方法。该项目将为量子退火器解决以下问题：是否存在描述所有当前量子退火硬件操作的局部隐藏变量理论？ 解决这个问题的理论工具包括离散系统的维格纳函数，它给出了一个和为1但可能为负的准概率的描述。当所有的准概率与状态，操作和测量是积极的，系统承认一个完全经典的隐变量描述。该团队将研究这种积极的经典描述对于量子退火机是否准确。

Quantum mechanics governs the behavior of the microscopic world, and its rules are very different from the laws of physics that are most familiar from everyday life. A scientific challenge of the 21st century is to harness the unique features of quantum mechanics for new technologies. For example, a computer that works on the basis of quantum logic would offer speed-ups and other advantages when compared with familiar classical computers, at least for some nearly intractable computational problems. Another type of machine called a quantum annealer can be used to solve optimization problems. While not a full-fledged quantum computer, a quantum annealer uses tunneling and entanglement during its operation, and its advantages over conventional machines is a topic of much current research. This project will attempt to show that the restrictions present in current quantum annealers mean that these machines are not yet sufficiently quantum mechanical to provide a fundamental computational advantage over conventional computation methods. If successful, this work will make clear that proposed modifications to current annealers, which are technologically feasible, are necessary for these devices to provide useful improvements over conventional computing approaches. If this claim is not proven, this work may provide insights into when current quantum annealers can be expected to outperform conventional computers.Quantum computation promises advantages over classical computation for certain problems. However, the experimental obstacles to the construction of a large scale quantum computer are formidable. Quantum annealing is an intermediate approach to obtaining some quantum advantage, and over the last decade it has been implemented on a reasonably large scale. Quantum annealers solve optimization problems, and there is experimental evidence for quantum effects such as tunneling and entanglement during their operation. A general theory of when these machines provide a quantum advantage is absent, but because of the existence of actual hardware a large body of empirical knowledge is accumulating about their operation. This work will address whether they can provide a uniquely quantum advantage over classical approaches. The project will address the following question for quantum annealers: Is there a local hidden variable theory that describes the operation of all current quantum annealing hardware? Theoretical tools to address this question include Wigner functions for discrete systems that give a description in terms of quasi-probabilities that sum to one, but which may be negative. When all the quasi-probabilities associated with states, operations and measurements are positive, the system admits a completely classical hidden variable description. This team will investigate whether such a positive, classical description can be accurate for quantum annealers.