Much of the recent attention directed towards topological insulators is motivated by their hallmark feature of protected chiral edge states. In electronic (or fermionic) topological insulators, these states originate from time-reversal symmetry and allow carriers with opposite spin-polarization to propagate in opposite directions at the edge of an insulating bulk. By contrast, photonic (or bosonic) systems are generally assumed to be precluded from supporting edge states that are intrinsically protected by time-reversal symmetry. Here, we experimentally demonstrate counter-propagating chiral states at the edge of a time-reversal-symmetric photonic waveguide structure. The pivotal step in our approach is the design of a Floquet driving protocol that incorporates effective fermionic time-reversal symmetry, enabling the realization of the photonic version of an electronic topological insulator. Our findings allow for fermionic properties to be harnessed in bosonic systems, thereby offering alternative opportunities for photonics as well as acoustics, mechanical waves and cold atoms.

最近对拓扑绝缘体的关注主要是受其受保护的手性边缘态特征的推动。在电子（或铁电离子）拓扑绝缘体中，这些状态源自时间反转对称性，并允许具有相反自旋极化的载流子在绝缘块的边缘沿相反方向传播。相比之下，通常假定光子（或玻色子）系统不具有受时间反转对称性固有保护的支撑边缘状态。在这里，我们通过实验证明了时间反向对称光子波导结构边缘处的反向传播手性态。我们方法中的关键步骤是Floquet驱动协议的设计，该协议融合了有效的费米电子时间反转对称性，实现电子拓扑绝缘体的光子版本。我们的发现允许在玻色子系统中利用费米子性质，从而为光子学以及声学，机械波和冷原子提供了替代机会。