Meltdown in quantum computers needs not occur: Nuclear experiments show   a way out
  We show that phase memory can be much longer than energy relaxation in systems with exponentially large dimensions of Hilbert space; this finding is documented by fifty years of nuclear experiments, though the information is somewhat hidden. For quantum computers Hilbert spaces of dimension $2^{100}$ or larger will be typical and therefore this effect may contribute significantly to reduce the problems of scaling of quantum computers to a useful number of qubits. 
J. Flores, S.Yu. Kun, T.H. Seligman