  Based on numerically-optimized real-device gates and parameters we study the
performance of the phase-flip (repetition) code on a linear array of Gallium
Arsenide (GaAs) quantum dots hosting singlet-triplet qubits. We first examine
the expected performance of the code using simple error models of circuit-level
and phenomenological noise, reporting, for example, a circuit-level
depolarizing noise threshold of approximately 3%. We then perform
density-matrix simulations using a maximum-likelihood and minimum-weight
matching decoder to study the effect of real-device dephasing, read-out error,
quasi-static as well as fast gate noise. Considering the trade-off between
qubit read-out error and dephasing time (T2) over measurement time, we identify
a sub-threshold region for the phase-flip code which lies within experimental
reach.
