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Maintaining coherence in Quantum Computers

W. G. Unruh
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Abstract

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.

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W. G. Unruh. 1994-06-09. Maintaining coherence in Quantum Computers. https://doi.org/10.1103/physreva.51.992

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