  The unconstrained classical system equivalent to spatially homogeneous SU(2)
Yang-Mills theory with theta angle is obtained and canonically quantized. The
Schr\"odinger eigenvalue problem is solved approximately for the low lying
states using variational calculation. The properties of the groundstate are
discussed, in particular its electric and magnetic properties, and the value of
the "gluon condensate" is calculated. Furthermore it is shown that the energy
spectrum of SU(2) Yang-Mills quantum mechanics is independent of the theta
angle. Explicit evaluation of the Witten formula for the topological
susceptibility gives strong support for the consistency of the variational
results obtained.
