  We present measurements of the phase coherence time $\tau_\phi$ in six
quasi-1D Au wires and clearly show that $\tau_\phi$ is temperature independent
at low temperatures. We suggest that zero-point fluctuations of the intrinsic
electromagnetic environment are responsible for the observed saturation of
$\tau_\phi$. We introduce a new functional form for the temperature dependence
and present the results of a calculation for the saturation value of
$\tau_\phi$. This explains the observed temperature dependence of our samples
as well as many 1D and 2D systems reported to date.
