Wednesday, April 25, 2012

1111.3965 (J. Eisert et al.)

Quantum measurement occurrence is undecidable    [PDF]

J. Eisert, M. P. Mueller, C. Gogolin
In this work, we show that very natural, apparently simple problems in quantum measurement theory can be undecidable even if their classical analogues are decidable. Undecidability hence appears as a genuine quantum property here. Formally, an undecidable problem is a decision problem for which one cannot construct a single algorithm that will always provide a correct answer in finite time. The problem we consider is to determine whether sequentially used identical Stern-Gerlach-type measurement devices, giving rise to a tree of possible outcomes, have outcomes that never occur. Finally, we point out implications for measurement-based quantum computing and studies of quantum many-body models and suggest that a plethora of problems may indeed be undecidable.
View original: http://arxiv.org/abs/1111.3965

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