(2+1)D格点规范理论中电荷与弦动力学的可视化
Visualizing Dynamics of Charges and Strings in (2+1)D Lattice Gauge Theories
AI总结：
本研究利用超导量子比特二维晶格模拟$\mathbb{Z}_2$格点规范理论中局部电荷激发的量子动力学，实验成像了弦动力学，揭示了禁闭相内弱强禁闭的横向涨落差异，并展示了促进动力学弦断裂的共振条件。
摘要：
格点规范理论可用于理解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等广泛现象。研究涌现相的动力学性质极具挑战性，因为这需要求解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研究了$\mathbb{Z}_2$ LGT中局部激发的动力学。我们首先构建了一个简单的变分量子电路，用于制备与基态有极大重叠的低能态；随后通过局部量子门创建电荷激发，并利用离散时间演化模拟其量子动力学。随着电场耦合常数增加，我们的测量结果显示出从退禁闭动力学向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发了张力。该方法使我们能够在(2+1)D LGT中实验性地成像弦动力学，并由此揭示了禁闭相内存在的两个不同区域：在弱禁闭下，弦在横向方向上强烈涨落；而在强禁闭下，横向涨落被有效冻结。此外，我们展示了一种可促进动力学弦断裂的共振条件。我们在量子处理器上的LGT实现，为研究涌现激发与弦动力学提供了一套新技术。
英文摘要：
Lattice gauge theories (LGTs) can be employed 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 $\mathbb{Z}_2$ LGT using a two-dimensional lattice of superconducting qubits. We first construct a simple variational circuit which 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 via 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, while for strong confinement transverse fluctuations are effectively frozen. In addition, we demonstrate a resonance condition at which dynamical string breaking is facilitated. Our LGT implementation on a quantum processor presents a novel set of techniques for investigating emergent excitations and string dynamics.
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