Are random pure States useful for quantum computation?

Phys Rev Lett

Department of Computer Science, University of Bristol, Bristol BS8 1UB, United Kingdom.

Published: May 2009

We show the following: a randomly chosen pure state as a resource for measurement-based quantum computation is-with overwhelming probability-of no greater help to a polynomially bounded classical control computer, than a string of random bits. Thus, unlike the familiar "cluster states," the computing power of a classical control device is not increased from P to BQP (bounded-error, quantum polynomial time), but only to BPP (bounded-error, probabilistic polynomial time). The same holds if the task is to sample from a distribution rather than to perform a bounded-error computation. Furthermore, we show that our results can be extended to states with significantly less entanglement than random states.

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http://dx.doi.org/10.1103/PhysRevLett.102.190502DOI Listing

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