  We report magnetotransport measurements of two-dimensional holes in open
quantum dots, patterned either as a single-dot or an array of dots, on a GaAs
quantum well. For temperatures $T$ below 500 mK, we observe signatures of
coherent transport, namely, conductance fluctuations and weak antilocalization.
  From these effects, the hole dephasing time $\tau_\phi$ is extracted using
the random matrix theory. While $\tau_\phi$ shows a $T$-dependence that lies
between $T^{-1}$ and $T^{-2}$, similar to that reported for electrons, its
value is found to be approximately one order of magnitude smaller.
