An anomalous Floquet topological insulator (AFTI) is a periodically driven topological insulator (TI with nonzero winding numbers to support topological edge modes, though its standard topological invariants like Chern numbers are zero.
The photonic lattice constructed by an optical waveguide array fabricated by the femtosecond laser direct writing (FLDW) is an important platform for quantum simulation to realize photonic AFTIs, because the FLDW offers flexible design of true three-dimensional (3D) waveguide structures and precise control of each coupling between waveguides. Moreover, the evolution distance of the lattice can be mapped as the evolution time.
In femtosecond-laser-direct-written photonic AFTIs, selective coupling of adjacent waveguides in a cycle is explicitly defined by the discrete periodically driving protocol. At the complete transfer discrete driving protocol, chiral edge modes co-exist with dispension-less bulk modes, and the lattice energy transfer efficiency of the chiral edge mode is the highest among all TIs (close to 100%), so it is very suitable for the transport of fragile quantum states.
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