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Comment on "Quantum waveguide array generator for performing Fourier transforms: Alternate route to quantum computing"
A Comment on the paper "Quantum waveguide array generator for performing
Fourier transforms: Alternate route to quantum computing" by R. Akis and D.K.
Ferry, Appl. Phys. Lett. 79, 2823 (2001). The authors reply in Appl. Phys.
Lett. 80, 2420 (2002).Comment: 1 pag
Symmetrizing Evolutions
We introduce quantum procedures for making -invariant the dynamics of
an arbitrary quantum system S, where is a finite group acting on the
space state of S. Several applications of this idea are discussed. In
particular when S is a N-qubit quantum computer interacting with its
environment and the symmetric group of qubit permutations, the
resulting effective dynamics admits noiseless subspaces. Moreover it is shown
that the recently introduced iterated-pulses schemes for reducing decoherence
in quantum computers fit in this general framework. The noise-inducing
component of the Hamiltonian is filtered out by the symmetrization procedure
just due to its transformation properties.Comment: Presentation improved, to appear in Phys. Lett. A. 5 pages LaTeX, no
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