11,644 research outputs found
Many Worlds, the Cluster-state Quantum Computer, and the Problem of the Preferred Basis
I argue that the many worlds explanation of quantum computation is not
licensed by, and in fact is conceptually inferior to, the many worlds
interpretation of quantum mechanics from which it is derived. I argue that the
many worlds explanation of quantum computation is incompatible with the
recently developed cluster state model of quantum computation. Based on these
considerations I conclude that we should reject the many worlds explanation of
quantum computation.Comment: Added doi, acknowledgements, miscellaneous typo correction
Can closed timelike curves or nonlinear quantum mechanics improve quantum state discrimination or help solve hard problems?
We study the power of closed timelike curves (CTCs) and other nonlinear
extensions of quantum mechanics for distinguishing nonorthogonal states and
speeding up hard computations. If a CTC-assisted computer is presented with a
labeled mixture of states to be distinguished--the most natural formulation--we
show that the CTC is of no use. The apparent contradiction with recent claims
that CTC-assisted computers can perfectly distinguish nonorthogonal states is
resolved by noting that CTC-assisted evolution is nonlinear, so the output of
such a computer on a mixture of inputs is not a convex combination of its
output on the mixture's pure components. Similarly, it is not clear that CTC
assistance or nonlinear evolution help solve hard problems if computation is
defined as we recommend, as correctly evaluating a function on a labeled
mixture of orthogonal inputs.Comment: 4 pages, 3 figures. Final version. Added several references, updated
discussion and introduction. Figure 1(b) very much enhance
ICGC-2004 Conference Overview
This is a written, expanded version of the summary talk given at the
conclusion of the ICGC-2004 held at Cochin. Brief introductory remarks are
included to provide a slightly wider context to the theme talks.Comment: 14 pages, revtex4, no figure
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