Investigating the Microscopic Origins of Loss in Superconducting Qubits

Abstract

The superconducting qubit is an especially promising platform in the pursuit of a near-term quantum computer. Over the past two decades, developments in superconducting qubits have allowed researchers to demonstrate robust quantum error correction, quantum algorithm execution, and quantum supremacy. One barrier towards further development is the T1 relaxation time, or the lifetime of the qubit; longer T1 times would enable complex computations with opportunities ranging from quantum chemistry to useful algorithms such as Shor’s. Today, loss in devices is consistently three orders of magnitude worse than the limits imposed by bulk constituent materials, pointing to an opportunity for enormous improvements through understanding and mitigating microscopic origins of noise. We first establish a framework for loss characterization through use of superconducting coplanar waveguide resonators, finding loss in our devices to be robustly explained by two-level systems and equilibrium quasiparticles. In the following chapters, we motivate and begin testing loss mitigation hypotheses through manipulations of the material platform.