Investigation of the loss budget in superconducting transmon qubits

Various energy loss mechanisms, such as dielectric loss, radiative loss, and quasiparticle generation, fundamentally constrain the coherence time of superconducting qubits. In this work, we discuss the so-called loss budget, i.e., identification and quantification of these mechanisms, based on the extensive investigations on dielectric characterizations, superconducting cavity and qubit measurements, and energy participation ratio simulations. We present an overview of the primary sources contributing to the loss budget, highlighting our recent advances in material engineering, device designs, and nanofabrication techniques to mitigate these losses. Significant improvements in qubit lifetimes are achievable by reducing these decoherence sources, paving the way for robust and scalable quantum processors.