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Google Research, Mountain View, CA, USA.
Department of Physics, Princeton University, Princeton, NJ, USA.
Nature. 2025 Jun;642(8067):315-320. doi: 10.1038/s41586-025-08999-9. Epub 2025 Jun 4.
Lattice gauge theories (LGTs) can be used to understand a wide range of phenomena, from elementary particle scattering in high-energy physics to effective descriptions of many-body interactions in materials. Studying dynamical properties of emergent phases can be challenging, as it requires solving many-body problems that are generally beyond perturbative limits. Here we investigate the dynamics of local excitations in a LGT using a two-dimensional lattice of superconducting qubits. We first construct a simple variational circuit that prepares low-energy states that have a large overlap with the ground state; then we create charge excitations with local gates and simulate their quantum dynamics by means of a discretized time evolution. As the electric field coupling constant is increased, our measurements show signatures of transitioning from deconfined to confined dynamics. For confined excitations, the electric field induces a tension in the string connecting them. Our method allows us to experimentally image string dynamics in a (2+1)D LGT, from which we uncover two distinct regimes inside the confining phase: for weak confinement, the string fluctuates strongly in the transverse direction, whereas for strong confinement, transverse fluctuations are effectively frozen. We also demonstrate a resonance condition at which dynamical string breaking is facilitated. Our LGT implementation on a quantum processor presents a new set of techniques for investigating emergent excitations and string dynamics.
格点规范理论（LGTs）可用于理解广泛的现象，从高能物理中的基本粒子散射到材料中多体相互作用的有效描述。研究涌现相的动力学性质可能具有挑战性，因为这需要解决通常超出微扰极限的多体问题。在此，我们使用超导量子比特的二维晶格来研究格点规范理论中局部激发的动力学。我们首先构建一个简单的变分电路，制备与基态有很大重叠的低能态；然后我们用局部门创建电荷激发，并通过离散时间演化模拟它们的量子动力学。随着电场耦合常数的增加，我们的测量结果显示出从解禁闭到禁闭动力学转变的特征。对于禁闭激发，电场在连接它们的弦中诱导出张力。我们的方法使我们能够在（2 + 1）维格点规范理论中对弦动力学进行实验成像，从中我们发现了禁闭相内的两种不同状态：对于弱禁闭，弦在横向方向强烈波动，而对于强禁闭，横向波动有效地被冻结。我们还展示了一个促进动态弦断裂的共振条件。我们在量子处理器上对格点规范理论的实现为研究涌现激发和弦动力学提供了一套新的技术。
