Comparative definitions of the condition number in Stokes polarimetry

In polarimetry, the condition number defines the stability and noise sensitivity that a
polarimeter can achieve, being a key factor to understand its performance. In this work,
we numerically calculate the error obtained for Stokes polarimetry with different number
of measurements and optimization strategies. Using these results, we show that not all
definitions and metrics used in the scientific literature to calculate the condition numbers
are physically robust and metrologically significant, and propose the best ones for predicting
the error in Stokes polarimetry. The selected definitions imply norms based on the singular
value decomposition of the inverse, or pseudo inverse, of the instrument matrix associated
to the measurement procedure.