  We propose and implement a non-destructive measurement that distinguishes
between two-electron spin states in a quantum dot. In contrast to earlier
experiments with quantum dots, the spins are left behind in the state
corresponding to the measurement outcome. By measuring the spin states twice
within a time shorter than the relaxation time, T1, correlations between
consecutive measurements are observed. They disappear as the wait time between
measurements become comparable to T1. The correlation between the
post-measurement state and the measurement outcome is measured to be ~90% on
average.
