  We present efficient methods to reliably characterize and tune gate-defined
semiconductor spin qubits. Our methods are designed to target the tuning
procedures of semiconductor double quantum dot in GaAs heterostructures, but
can easily be adapted to other quantum-dot-like qubit systems. These tuning
procedures include the characterization of the inter-dot tunnel coupling, the
tunnel coupling to the surrounding leads and the identification of the various
fast initialization points for the operation of the qubit. Since
semiconductor-based spin qubits are compatible with standard semiconductor
process technology and hence promise good prospects of scalability, the
challenge of efficiently tuning the dot's parameters will only grow in the near
future, once the multi-qubit stage is reached. With the anticipation of being
used as the basis for future automated tuning protocols, all measurements
presented here are fast-to-execute and easy-to-analyze characterization
methods. They result in quantitative measures of the relevant qubit parameters
within a couple of seconds, and require almost no human interference.
