论文标题
迈向材料的近期量子模拟
Towards near-term quantum simulation of materials
论文作者
论文摘要
材料的模拟是量子计算机最有希望的应用之一。在近期硬件上,这些模拟的关键限制是电路深度。许多量子模拟算法都依赖于哈密顿量中每个术语产生的一层单一演变。这在时间动力学中是一个单个猪排步骤,在汉密尔顿变异的Ansatz下作为单个ANSATZ层的变异量子本质体。我们为材料建模提供了一种新的量子算法设计,其中一层的深度与系统大小无关。该设计利用了材料的局部性,并采用了量身定制的费米语编码,可保留当地的地方。我们分析了这种方法的电路成本,并提出了将密度功能理论数据转换为量子电路指令的编译器 - 将材料的物理学连接到仿真电路。编译器会自动在多个级别上优化电路,从基本门水平到从特定目标材料的物理学得出的优化。我们为涵盖广泛结构和技术范围的材料提供了数值结果。我们的结果表明,与不考虑哈密顿式结构的标准先验方法相比,电路深度的许多数量级减少了。例如,我们的结果从864到180 QUBITS提高了盆地糊化酸盐的资源需求,以$ 3 \ times3 \ times3 $ lattice,以及单个猪排或各种层的电路深度从$ 7.5 \ times 10^8 $到深度$ 884 $ 884 $。尽管这仍然超出当前硬件的范围,但我们的结果表明,材料模拟在量子计算机上可能是可行的,而不必需要可扩展的,容忍故障的量子计算机提供的量子算法设计包含了对材料和应用的理解。
Simulation of materials is one of the most promising applications of quantum computers. On near-term hardware the crucial constraint on these simulations is circuit depth. Many quantum simulation algorithms rely on a layer of unitary evolutions generated by each term in a Hamiltonian. This appears in time-dynamics as a single Trotter step, and in variational quantum eigensolvers under the Hamiltonian variational ansatz as a single ansatz layer. We present a new quantum algorithm design for materials modelling where the depth of a layer is independent of the system size. This design takes advantage of the locality of materials in the Wannier basis and employs a tailored fermionic encoding that preserves locality. We analyse the circuit costs of this approach and present a compiler that transforms density functional theory data into quantum circuit instructions -- connecting the physics of the material to the simulation circuit. The compiler automatically optimises circuits at multiple levels, from the base gate level to optimisations derived from the physics of the specific target material. We present numerical results for materials spanning a wide structural and technological range. Our results demonstrate a reduction of many orders of magnitude in circuit depth over standard prior methods that do not consider the structure of the Hamiltonian. For example our results improve resource requirements for Strontium Vanadate (SrVO$_3$) from 864 to 180 qubits for a $3\times3\times3$ lattice, and the circuit depth of a single Trotter or variational layer from $7.5\times 10^8$ to depth $884$. Although this is still beyond current hardware, our results show that materials simulation may be feasible on quantum computers without necessarily requiring scalable, fault-tolerant quantum computers, provided quantum algorithm design incorporates understanding of the materials and applications.