Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.
Munich Center for Quantum Science and Technology (MCQST), 80799 Munich, Germany.
Science. 2022 May 13;376(6594):716-720. doi: 10.1126/science.abk2397. Epub 2022 May 12.
The Kardar-Parisi-Zhang (KPZ) universality class describes the coarse-grained behavior of a wealth of classical stochastic models. Surprisingly, KPZ universality was recently conjectured to also describe spin transport in the one-dimensional quantum Heisenberg model. We tested this conjecture by experimentally probing transport in a cold-atom quantum simulator via the relaxation of domain walls in spin chains of up to 50 spins. We found that domain-wall relaxation is indeed governed by the KPZ dynamical exponent = 3/2 and that the occurrence of KPZ scaling requires both integrability and a nonabelian SU(2) symmetry. Finally, we leveraged the single-spin-sensitive detection enabled by the quantum gas microscope to measure an observable based on spin-transport statistics. Our results yield a clear signature of the nonlinearity that is a hallmark of KPZ universality.
Kardar-Parisi-Zhang (KPZ) 普遍性类描述了大量经典随机模型的粗粒化行为。令人惊讶的是，最近有人推测 KPZ 普遍性也描述了一维量子海森堡模型中的自旋输运。我们通过在冷原子量子模拟器中通过自旋链中的畴壁弛豫来探测输运，从而验证了这一推测，其中自旋链的长度最多可达 50 个自旋。我们发现，畴壁弛豫确实由 KPZ 动力学指数 = 3/2 控制，并且 KPZ 标度的发生既需要可积性，也需要非阿贝尔 SU(2)对称性。最后，我们利用量子气体显微镜实现的单自旋敏感探测，测量了基于自旋输运统计的可观测量。我们的结果清楚地显示了 KPZ 普遍性的非线性特征。
