  We present a versatile design of freely suspended quantum point contacts with
particular large one-dimensional subband quantization energies of up to 10meV.
The nanoscale bridges embedding a two-dimensional electron system are
fabricated from AlGaAs/GaAs heterostructures by electron-beam lithography and
etching techniques. Narrow constrictions define quantum point contacts that are
capacitively controlled via local in-plane side gates. Employing transport
spectroscopy, we investigate the transition from electrostatic subbands to
Landau-quantization in a perpendicular magnetic field. The large subband
quantization energies allow us to utilize a wide magnetic field range and
thereby observe a large exchange splitted spin-gap of the two lowest
Landau-levels.
