Wang Guoqing, Li Changhao, Cappellaro Paola
Research Laboratory of Electronics and Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2021 Oct 1;127(14):140604. doi: 10.1103/PhysRevLett.127.140604.
Periodically driven (Floquet) quantum systems have recently been a focus of nonequilibrium physics by virtue of their rich dynamics. Time-periodic systems not only exhibit symmetries that resemble those in spatially periodic systems, but also display novel behavior that arises from symmetry breaking. Characterization of such dynamical symmetries is crucial, but often challenging due to limited driving strength and lack of an experimentally accessible characterization technique. Here, we show how to reveal dynamical symmetries, namely, parity, rotation, and particle-hole symmetries, by observing symmetry-induced Floquet selection rules. Notably, we exploit modulated driving to reach the strong light-matter coupling regime, and we introduce a protocol to experimentally extract the transition matrix elements between Floquet states from the system coherent evolution. By using nitrogen-vacancy centers in diamond as an experimental test bed, we execute our protocol to observe symmetry-protected dark states and dark bands, and coherent destruction of tunneling. Our work shows how one can exploit the quantum control toolkit to study dynamical symmetries that arise in the topological phases of strongly driven Floquet systems.
周期性驱动（弗洛凯）量子系统因其丰富的动力学特性，近来成为非平衡态物理学的一个研究焦点。时间周期系统不仅展现出与空间周期系统相似的对称性，还呈现出由对称性破缺产生的新奇行为。表征此类动力学对称性至关重要，但由于驱动强度有限以及缺乏实验上可实现的表征技术，这一过程往往具有挑战性。在此，我们展示了如何通过观察对称性诱导的弗洛凯选择规则来揭示动力学对称性，即宇称、旋转和粒子 - 空穴对称性。值得注意的是，我们利用调制驱动进入强光 - 物质耦合 regime ，并引入一种实验方案，从系统的相干演化中提取弗洛凯态之间的跃迁矩阵元。通过将金刚石中的氮空位中心用作实验测试平台，我们执行该方案以观测对称性保护的暗态和暗带，以及隧穿的相干破坏。我们的工作展示了如何利用量子控制工具包来研究强驱动弗洛凯系统拓扑相中的动力学对称性。
