  In this paper, I present a simple method of obtaining spin-polarised current
from a QPC with a large Rashba interaction. The origin of this spin
polarisation is the adiabatic evolution of spin "up" of the first QPC sub-band,
into spin "down" of the second QPC sub-band. Unique experimental signatures of
this effect can be obtained using a magnetic focusing setup, with the
characteristic "double" peak of spin-split magnetic focusing only present for
conductances $G>2e^2/h$. These particular magnetic focusing features are
present in recently publish experimental results. Finally, I consider hole
QPCs, where due to the particular kinematic structure of the Rashba
interaction, the required parameters are much less favourable for experimental
realisation.
