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I have been thinking about Spekkens Toy model in terms of interfaces. The Spekkens paper concerns a physics based on only being able to receive answers to half the number of questions necessary to specify the state of a system. This is something like having a limited interface to some kind of system. I take an apparatus as an internal category in a monoidal category and the apparatus is seen as some limited interface to an underlying quantum causal structure. Would it be possible to reformulate Spekkens' idea in terms of internal categories?

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up vote 4 down vote accepted

The short answer is yes: these ideas can be formulated as internal algebras in a monoidal category. Take a look at for starters. Bill Edwards' PhD thesis has quite a bit more, and other papers by him and Bob Coecke may also be of interest.

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Welcome to the site, Ross! – Joe Fitzsimons Dec 11 '11 at 17:56
Thanks Joe. I've been lurking since (before!) it started :-) – Ross Duncan Dec 11 '11 at 19:03

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