  We have studied ballistic transport in a 1D channel formed using surface gate
techniques on a back-gated, high-mobility, bilayer 2D hole system. At
millikelvin temperatures, robust conductance quantization is observed in the
quantum wire formed in the top layer of the bilayer system, without the gate
instabilities that have hampered previous studies of 1D hole systems. Using
source drain bias spectroscopy, we have measured the 1D subband spacings, which
are 5-10 times smaller than in comparable GaAs electron systems, but 2-3 times
larger than in previous studies of 1D holes. We also report the first
observation of the anomalous conductance plateau at G = 0.7 x 2e2/h in a 1D
hole system.
