  The temperature and magnetic-field dependences of the resistance of
one-dimensional (1D) conductors have been studied in the vicinity of the
Thouless crossover. We find that on the weak localization (WL) side of the
crossover, these dependences are consistent with the theory of quantum
corrections to the resistance, and the phase breaking is due to the
quasi-elastic electron-electron interactions (the Nyquist noise). The
temperature dependence of the phase coherence time does not saturate, and the
quasiparticle states remain well defined over the whole WL temperature range.
This fact, as well as observation of the Thouless crossover in 1D samples,
argues against the idea of intrinsic decoherence by zero-point fluctuations of
the electrons (Mohanty et al., Phys.Rev.Lett. 78, 3366 (1997)). We believe that
frequently observed saturation of the phase coherence time is caused by the
external microwave noise.
