  $\textbf{scqubits}$ is an open-source Python package for simulating and
analyzing superconducting circuits. It provides convenient routines to obtain
energy spectra of common superconducting qubits, such as the transmon,
fluxonium, flux, cos(2$\phi$) and the 0-$\pi$ qubit. $\textbf{scqubits}$ also
features a number of options for visualizing the computed spectral data,
including plots of energy levels as a function of external parameters, display
of matrix elements of various operators as well as means to easily plot qubit
wavefunctions. Many of these tools are not limited to single qubits, but extend
to composite Hilbert spaces consisting of coupled superconducting qubits and
harmonic (or weakly anharmonic) modes. The library provides an extensive suite
of methods for estimating qubit coherence times due to a variety of commonly
considered noise channels. While all functionality of $\textbf{scqubits}$ can
be accessed programatically, the package also implements GUI-like widgets that,
with a few clicks can help users both create relevant Python objects, as well
as explore their properties through various plots. When applicable, the library
harnesses the computing power of multiple cores via multiprocessing.
$\textbf{scqubits}$ further exposes a direct interface to the Quantum Toolbox
in Python (QuTiP) package, allowing the user to efficiently leverage QuTiP's
proven capabilities for simulating time evolution.
