  Single-top-quark production probes the charged-current weak interaction of
the top quark, and provides a direct measurement of the CKM matrix element
V_{tb}. We perform two independent analyses to quantify the accuracy with which
the W-gluon fusion (gq -> t\bar{b}q) and (q\bar{q} -> t\bar{b}) signals can be
extracted from the backgrounds at both the Tevatron and the LHC. Although
perturbation theory breaks down at low transverse momentum for the W-gluon
fusion \bar{b} differential cross section, we show how to obtain a reliable
cross section integrated over low \bar{b} transverse momenta up to a cutoff. We
estimate the accuracy with which V_{tb} can be measured in both analyses,
including theoretical and statistical uncertainties. We also show that the
polarization of the top quark in W-gluon fusion can be detected at the Fermilab
Tevatron and the CERN LHC.
