  The progress witnessed within the field of quantum computing has been enabled
by the identification and understanding of interactions between the state of
the quantum bit (qubit) and the materials within its environment. Beginning
with an introduction of the parameters used to differentiate various quantum
computing approaches, we discuss the evolution of the key components that
comprise superconducting qubits, where the methods of fabrication can play as
important a role as the composition in dictating the overall performance. We
describe several mechanisms that are responsible for the relaxation or
decoherence of superconducting qubits and the corresponding methods that can be
utilized to characterize their influence. In particular, the effects of
dielectric loss and its manifestation through the interaction with two-level
systems (TLS) are discussed. We elaborate on the methods that are employed to
quantify dielectric loss through the modeling of energy flowing through the
surrounding dielectric materials, which can include contributions due to both
intrinsic TLS and extrinsic aspects, such as those generated by processing. The
resulting analyses provide insight into identifying the relative participation
of specific sections of qubit designs and refinements in construction that can
mitigate their impact on qubit quality factors. Additional prominent mechanisms
that can lead to energy relaxation within qubits are presented along with
experimental techniques which assess their importance. We close by highlighting
areas of future research that should be addressed to help facilitating the
successful scaling of superconducting quantum computing.
