Quantum acoustodynamics with a fluxonium qubit*

Quantum states of mechanical motion offer the potential to realize long lived multimodal quantum memories as well as quantum transduction between disparate quantum systems.  Surface acoustic wave (SAW) devices in particular provide customizable long-on chip delays for realizing a multimodal system.  Most previous quantum acoustic SAW devices have utilized a transmon qubit, necessitating operation at several gigahertz where the qubit has significant anharmonicity.  Here, we integrate a 500 MHz SAW resonator with a fluxonium superconducting qubit.  This design provides a large anharmonicity at low frequency and long lived acoustic modes due to decreased bulk scattering losses at low frequency.  We demonstrate acoustic modes with linewidths of 1.5 kHz.  Our design uses flip chip indium bump bonding, intended to increase qubit performance by removing the fluxonium qubit from the piezoelectric quartz medium and instead placing it on sapphire.  This device is positioned to investigate quantum acoustodynamics in the multi-mode, strong dispersive regime.