  \DeclareRobustCommand{\pbar}{\HepAntiParticle{p}{}{}\xspace}
\DeclareRobustCommand{\p}{\HepParticle{p}{}{}\xspace}
\DeclareRobustCommand{\mup}{$\mu_{p}${}{}\xspace}
\DeclareRobustCommand{\mupbar}{$\mu_{\pbar}${}{}\xspace}
\DeclareRobustCommand{\muN}{$\mu_N${}{}\xspace
  For the first time a single trapped \pbar is used to measure the \pbar
magnetic moment ${\bm\mu}_{\pbar}$. The moment ${\bm\mu}_{\pbar} = \mu_{\pbar}
{\bm S}/(\hbar/2)$ is given in terms of its spin ${\bm S}$ and the nuclear
magneton (\muN) by $\mu_{\pbar}/\mu_N = -2.792\,845 \pm 0.000\,012$. The 4.4
parts per million (ppm) uncertainty is 680 times smaller than previously
realized. Comparing to the proton moment measured using the same method and
trap electrodes gives $\mu_{\pbar}/\mu_p = -1.000\,000 \pm 0.000\,005$ to 5
ppm, for a proton moment ${\bm{\mu}}_{p} = \mu_{p} {\bm S}/(\hbar/2)$,
consistent with the prediction of the CPT theorem.
