  Random and uncontrollable noises from the environment during the design and
measurement of superconducting qubits lead to limitations in qubit coherence
time and gate fidelity, which is a major challenge in the current state of the
art for superconducting quantum computing. To advance superconducting qubits
technologies it is essential to understand and mitigate environmentally induced
errors. This requires modeling superconducting qubits as open quantum systems
coupled to their surroundings. The present study aims to provide useful open
quantum system approaches to analyze and quantify the interaction between the
superconducting qubits and their environment. We provide an accessible
introduction to open quantum systems for newcomers to the field. For experts we
discuss recently developed methods for analyzing qubit dynamics under realistic
noises. We outline how these techniques provide quantitative insights into the
decoherence mechanism and how they can guide design improvements to enhance
qubits' coherence time. This self-contained review of open quantum system
approaches can be used to model, understand, and improve superconducting qubit
performance in the presence of unavoidable environmental noises.
