  We experimentally study quantized conductance in an electrostatically defined
constriction in a high-mobility InAs two-dimensional electron gas. A parallel
magnetic field lifts the spin degeneracy and allows for the observation of
plateaus in integer multiples of $e^2/h$. Upon the application of a
perpendicular magnetic field, spin-resolved magnetoelectric subbands are
visible. Through finite bias spectroscopy we measure the subband spacings in
both parallel and perpendicular direction of the magnetic field and determine
the $g$-factor.
