Quantum simulation algorithms for quantum chromodynamics

量子色动力学(QCD)是强力理论，它是我们理解大量实验观测以及预测在欧洲核子研究中心LHC等对撞机实验中发现新粒子的核心。阻碍QCD成功应用于实际系统的主要突出问题之一是其固有的计算复杂性。许多重要的问题都不愿重复寻找有效的经典算法来洞察物质的基本组成部分的行为。这自然会让我们考虑其他有潜力克服上述障碍的计算范例，如量子计算。1982年，费曼提出在经典计算机上模拟一般多体量子系统的演化需要指数级资源，这标志着量子计算的出现。这是由于底层希尔伯特空间的维度随着系统大小的指数缩放。相反，正如费曼所观察到的，量子系统本身的演化只需要多项式开销。从那时起，在处理量子信息方面取得了稳步的理论进展，这刺激了新的信息处理协议的发展，这些协议本质上依赖于物理系统的量子性质，并为可扩展的量子计算机提供应用。目前，正在进行一项重大的理论和实验工作，以期真正建造中小型量子计算机。这一点，加上切实的实验进展，不仅为新的算法进步开辟了道路，也为量子理论在一系列以前无法解决的问题上的定制应用开辟了道路。我们的目标是利用量子计算和物理系统模拟的最新进展来解决QCD中以前用传统经典方法难以解决的问题。这将使我们能够更深入地研究粒子相互作用，并启发出新的有效的量子方法来模拟自然力的基本力。

Quantum Chromodynamics (QCD) is the theory of strong force and it lies at the heart of our understanding of the plethora of experimental observations, as well as predictions for new particle discoveries in collider experiments like LHC at CERN. One of the major outstanding problems that stand in the way of the successful application of the QCD to real-world systems is its inherent computational complexity. Many important problems resist repeated efforts to find efficient classical algorithms to gain insight into the behaviour of basic building blocks of matter. This naturally leads us to consider other promising computational paradigms that have a potential to overcome the above obstacles such as quantum computing. The emergence of quantum computing was marked by Feynman's insight in 1982 that simulating the evolution of general many-body quantum systems on a classical computer requires exponential resources. This is due to the exponential scaling of the dimension of the underlying Hilbert space with the system size. In contrast, as Feynman observed, the evolution of the quantum system itself requires only polynomial overhead. Since then, there has been steady theoretical progress on manipulation of quantum information and this has stimulated the development of new information processing protocols which rely essentially on the quantum nature of the physical systems and provide applications for scalable quantum computers. Currently, there is a major theoretical and experimental effort towards actually building small to medium-sized quantum computers. This, together with tangible experimental advances opens up avenues not only for novel algorithmic advances but also for bespoke applications of quantum theory to a range of problems that were previously inaccessible.We aim to exploit recent advances in quantum computing and simulation of physical systems to solve problems in QCD that were previously intractable by traditional classical methods. This will allow us to delve deeper into particle interaction and inspire new efficient quantum methods for simulating fundamental forces of nature.