Mitigating Superconducting Qubit Loss by Active Acoustic Pumping

One promising candidate for building quantum computers is superconducting qubits. These qubits experience significant loss via two-level system (TLS) material defects. There are various approaches to reducing TLS loss such as enhancing substrate materials and improving nanofabrication techniques, as well as circuit designs that reduce the participation of dielectrics hosting defects. Here we investigate a different, less commonly explored option — active cancellation of TLS-induced dissipation using surface acoustic waves (SAWs). TLSs typically reside near substrate and metal surfaces and interact with strain fields, making SAW a promising approach to applying drives. Ideally, the superconducting circuit has no strain coupling and does not interact with the acoustic drive directly. In our device, SAWs are pumped into the silicon substrate containing a superconducting coplanar waveguide resonator using an interdigital transducer fabricated on localized thin-film aluminum nitride. The SAW drive modulates the TLS defects, interfering with the loss channel. We present experimental results and numerical simulations indicating that this kind of drive scheme can result in increased resonator lifetimes in the proper regime.