Phononic crystals in superfluid thin-film helium

This study of phononic crystals in thin-film superfluid helium presents an avenue for applications in quantum information processing and advanced sensing technologies, as it could enable precise control of sound waves at the quantum level. Progress here has been hampered by our limited understanding of phonon behavior in quantum fluids, plus the technical challenges of manipulating these waves in very cold superfluid helium. This research tackles these issues by implementing strong confinement of mechanical modes in superfluid thin films, using a phononic crystal structure. The work establishes a promising platform for achieving mechanical nonlinearities on the single-phonon level.