Characterizing Sources of Loss in Tantalum-Based Transmon Qubits

Abstract

As society continues to require increasing computational efficiency, quantum computers have gained relevance for a variety of computing applications. Reliable hardware implementations of quantum bits, or qubits, are currently impeded by decoherence that arises from the lossiness of the physical system. Understanding this decoherence, particularly from materials and circuit design perspectives, is critical both to the near-term scalability of quantum computers and the eventual realization of fault-tolerance in these systems. In this report we explore an approach to advance our understanding of the dominant loss channels in, and increase the coherence of, the superconducting transmon, a prominent forerunner among qubit hardware platforms. We analyze the formalism of the transmon and its predecessors, using existing literature to review quantitative models of its major loss mechanisms. Based on these models, we offer a method to help confirm which mechanisms are likely most dominant in the regimes in which we operate qubits, and provide justification for a potential increase in coherence. We outline future directions for, and natural extensions of, this project.