论文标题

具有高斯法律约束的2+1 U(1)晶格规定的有效量子实施

Efficient quantum implementation of 2+1 U(1) lattice gauge theories with Gauss law constraints

论文作者

Kane, Christopher, Grabowska, Dorota M., Nachman, Benjamin, Bauer, Christian W.

论文摘要

已知使用经典计算机对晶格量子场理论的实时演变进行研究,可以随晶格位点的数量成倍扩展。由于一种根本不同的计算策略,量子计算机的承诺允许从第一原理中详细研究这些动态。但是,与经典计算一样,量子算法的成本与体积成倍扩展很重要。最近,它显示了如何通过操作员重新定义在两个空间维度中在两个空间维度中打破U(1)量规理论的指数缩放。在这项工作中,我们描述了如何在新操作员基础上对操作员进行采样以保持数字化错误较小的修改。我们比较了两个操作员群之间的能量和plaquette期望值的精度,并发现它们是可比的。此外,我们还使用WALSH函数形式主义提供了理论的铃木 - 漫游实施的明确电路构建。对于精确的电路和近似电路,将栅极计数的缩放缩放为晶格体积的函数,其中丢弃了带有小参数的旋转门。我们在使用IBMQ超导置换量硬件的明确观察到的明确观察到的计算中研究了有限的Suzuki-Trotter时步,电路近似和量子噪声的错误。我们发现,可以通过不引入较大错误的情况下将近似电路的栅极计数缩放缩放到体积的功率上。

The study of real-time evolution of lattice quantum field theories using classical computers is known to scale exponentially with the number of lattice sites. Due to a fundamentally different computational strategy, quantum computers hold the promise of allowing for detailed studies of these dynamics from first principles. However, much like with classical computations, it is important that quantum algorithms do not have a cost that scales exponentially with the volume. Recently, it was shown how to break the exponential scaling of a naive implementation of a U(1) gauge theory in two spatial dimensions through an operator redefinition. In this work, we describe modifications to how operators must be sampled in the new operator basis to keep digitization errors small. We compare the precision of the energies and plaquette expectation value between the two operator bases and find they are comparable. Additionally, we provide an explicit circuit construction for the Suzuki-Trotter implementation of the theory using the Walsh function formalism. The gate count scaling is studied as a function of the lattice volume, for both exact circuits and approximate circuits where rotation gates with small arguments have been dropped. We study the errors from finite Suzuki-Trotter time-step, circuit approximation, and quantum noise in a calculation of an explicit observable using IBMQ superconducting qubit hardware. We find the gate count scaling for the approximate circuits can be further reduced by up to a power of the volume without introducing larger errors.

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