  As the variety of commercially available quantum computers continues to
increase so does the need for tools that can characterize, verify and validate
these computers. This work explores using quantum state tomography for
characterizing the performance of individual qubits and develops a vector field
visualization for presentation of the results. The proposed protocol is
demonstrated in simulation and on quantum computing hardware developed by IBM.
The results identify qubit performance features that are not reflected in the
standard models of this hardware, indicating opportunities to improve the
accuracy of these models. The proposed qubit evaluation protocol is provided as
free open-source software to streamline the task of replicating the process on
other quantum computing devices.
