%0 Journal Article
%T Maintaining coherence in Quantum Computers
%A W. G. Unruh
%J Physics
%D 1994
%I arXiv
%R 10.1103/PhysRevA.51.992
%X The effect of the inevitable coupling to external degrees of freedom of a quantum computer are examined. It is found that for quantum calculations (in which the maintenance of coherence over a large number of states is important), not only must the coupling be small but the time taken in the quantum calculation must be less than the thermal time scale, $\hbar/k_B T$. For longer times the condition on the strength of the coupling to the external world becomes much more stringent.
%U http://arxiv.org/abs/hep-th/9406058v1