Reducing Quasiparticle-Induced Dissipation Using Gap-Engineering

Superconducting qubits based on Josephson junctions are a leading platform to implement universal quantum computing. However, non-equilibrium quasiparticles present challenges to scaling superconducting qubits because they can both degrade qubit lifetimes and generate correlated errors that compromise quantum error correction. To date, most approaches have focused on mitigating the generation of non-equilibrium quasiparticles, via shielding and filtering. In this talk, I will discuss a complementary approach that uses gap-engineering to mitigate the impact of non-equilibrium quasiparticle on chip. In particular, I will discuss progress toward the fabrication and measurement of transmon qubits with Josephson junctions that have spatially varying superconducting gap profiles in the leads.