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SUMMARY:Is Bell violation a necessary resource for non-trivial measurement
 -based computation? - Dan Browne (UCL)
DTSTART:20130530T131500Z
DTEND:20130530T141500Z
UID:TALK44435@talks.cam.ac.uk
CONTACT:William Matthews
DESCRIPTION:In measurement-based quantum computation\, adaptive single qub
 it measurement on a many-qubit entangled resource state (e.g. a cluster st
 ate) together with simple and efficient classical side-processing provides
  a model of computation equivalent to the quantum circuit model. A variety
  of entangled resource state families beyond the cluster states have been 
 proposed\, and it is natural to ask what roles the entanglement in these s
 tates is playing in the computation. To consider this\, we study measureme
 nt based computation on resource states with no entanglement or quantum di
 scord - essentially states which are equivalent to classical probability d
 istributions. We show that studying the computable functions in this model
  is equivalent to studying families CHSH-Bell inequalities\, and that the 
 lack of computational expressiveness in these models provides a compact un
 ified description of all CHSH-type inequalities. We then consider whether 
 these simple computations can still possess any non-classical attributes. 
 Surprisingly\, by modifying an argument of Bremner\, Shepherd and Josza\, 
 we can show among these computations exist uniform families which are unli
 kely to be exactly efficiently simulatable on a classical computation. The
 se computations - which can be cast as simple classical sampling problems 
 - form a subset of the families introduced by Bremner\, Shepherd and Josza
  and are striking for their simplicity.\n
LOCATION:MR13\, Centre for Mathematical Sciences
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