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CATEGORIES:CQIF Seminar
SUMMARY:Aharonov meets Spekkens: What do quantum paradoxe
s tell us about the nature of reality? - Matthew
Leifer (Perimeter Institute)
DTSTART;TZID=Europe/London:20151015T141500
DTEND;TZID=Europe/London:20151015T151500
UID:TALK61128AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/61128
DESCRIPTION:Over the last few decades\, Aharonov and collabora
tors have discovered a large number of counterintu
itive phenomena in quantum theory\, such as the "t
hree box paradox"\, the "quantum pigeonhole princi
ple"\, "quantum cheshire cats"\, and "protective m
easurement". The interpretation of these effects
has always been controversial\, with ongoing argum
ents about whether these effects have "classical"
analogues as opposed to being "genuinely quantum".
\n\nIn this talk\, I will reanalyse these effects
in light of the work of Spekkens. Spekkens emphas
izes that many seemingly strange quantum phenomena
actually have straightforward explanations if we
view quantum states as states of incomplete knowle
dge about some underlying reality. Those that do
not have such an explanation are the "genuinely qu
antum" phenomena\, and these all seem to fall unde
r the remit of Spekkens' generalized definition of
contextuality. So now we can make the question m
ore precise: can Aharonov's phenomena be explained
in theories in which the quantum state represents
incomplete knowledge and\, if not\, do they const
itute proofs of contextuality?\n\nI will show that
a class of effects known as "logical pre- and pos
t-selection paradoxes"\, which includes the three
box paradox and the quantum pigeonhole principle\,
do constitute direct proofs of contextuality\, so
they are "genuinely quantum" in Spekkens' sense.
On the other hand\, protective measurement\, whic
h was initially proposed as an argument for the re
ality of the quantum state\, is most easily accoun
ted for in theories in which the quantum state rep
resents incomplete knowledge.\n\nThis talk is base
d on joint work with Josh Combes\, Chris Ferrie\,
and Matt Pusey\, available in the papers arXiv:150
6.07850 and arXiv:1509.08893
LOCATION:MR4\, Centre for Mathematical Sciences\, Wilberfor
ce Road\, Cambridge
CONTACT:William Matthews
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