Toward a Universal Gate Set on a Qubit Encoded in Superconducting Cavities

Superconducting microwave cavities coupled to transmon ancillae are an attractive platform for the storage and manipulation of continuous variable (CV) quantum states. Each cavity is a bosonic mode that provides a long coherence time and a large Hilbert space that can be used to redundantly encode quantum information. The coupled transmon ancilla enables nearly arbitrary control over the state of each mode and can be used to perform high quality quantum nondemolition (QND) measurements of the cavity state. Further, it has been demonstrated that the nonlinearity of these ancilla transmons can be driven to enact parametric operations on the system, such as a bilinear coupling between two modes (Gao, et al., PRX 2018). Performing these operations with high fidelity requires mitigating dephasing effects arising from intrinsic properties of the transmon-cavity system as well as external drives. Here, we present our experimental progress towards mitigating these effects and enabling successive, high-fidelity pumped operations on states stored in these cavities.