  We propose and analyse a method for single shot measurement of the total spin
of a two electron system in a coupled quantum dot or donor impurity structure,
which can be used for readout in a quantum computer. The spin can be inferred
by observing spin dependent fluctuations of charge between the two sites, via a
nearby electrometer. Realistic experimental parameters indicate that the
fidelity of the measurement can be larger than 0.9999 with existing or
near-future technology.
