  We propose a method for the stabilisation of quantum computations (including
quantum state storage). The method is based on the operation of projection into
$\cal SYM$, the symmetric subspace of the full state space of $R$ redundant
copies of the computer. We describe an efficient algorithm and quantum network
effecting $\cal SYM$--projection and discuss the stabilising effect of the
proposed method in the context of unitary errors generated by hardware
imprecision, and nonunitary errors arising from external environmental
interaction. Finally, limitations of the method are discussed.
