Photonic topological boundary pumping as a probe of 4D quantum Hall physics

A 2D topological charge pump in a photonic waveguide array is used to observe boundary physics associated with the 4D quantum Hall effect experimentally. The quantum Hall effect, discovered in the 1980s, is an important fundamental effect in condensed matter physics that links topological states with electronic properties in two-dimensional systems. The quantized conductance is prescribed by an integer global topological invariant and is...