  Wave chaotic systems underpin a wide range of research activities, from
fundamental studies of quantum chaos via electromagnetic compatibility up to
more recently emerging applications like microwave imaging for security
screening, antenna characterisation or wave-based analog computation. To
implement a wave chaotic system experimentally, traditionally cavities of
elaborate geometries (bowtie shapes, truncated circles, parallelepipeds with
hemispheres) are employed because the geometry dictates the wave field's
characteristics. Here, we propose and experimentally verify a radically
different paradigm: a cavity of regular geometry but with tunable boundary
conditions, experimentally implemented by leveraging a reconfigurable
metasurface. Our results set new foundations for the use and the study of chaos
in wave physics.
