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Inaugural Conceptual and Historical Issues in Modern Physics (CHIMP) Meeting

Sydney :: Thursday 14 April 2005

Timetable : Abstracts : Venue : Registration


Click on titles for abstracts.

Are quantum states incomplete descriptions of reality?
Robert Spekkens


Quantum coherence:  fact or fiction?
Stephen Bartlett

Closing at 20:30.



Are quantum states incomplete descriptions of reality?
Robert Spekkens (Perimeter Institute for Theoretical Physics)

What would it be like to live in a world where observers were faced with a fundamental restriction on how much knowledge they could acquire about the states of systems around them? I attempt to answer this question in a particularly simple context, where an observer's knowledge is characterized by a number of yes/no questions, and where the restriction on knowledge has a particularly simple form: the number of questions that are answered is always less than or equal to the number of questions that are unanswered. Remarkably, given a few other assumptions about this toy universe, one obtains a richly structured theory that qualitatively reproduces a wide variety of quantum phenomena. Such phenomena include the noncommutativity of measurements, the impossibility of discriminating non-orthogonal states, interference, various features of entanglement, the no cloning theorem, quantum teleportation, and many others. The quality and diversity of these analogies provides compelling evidence for the view that quantum states are states of incomplete knowledge rather than states of reality. A consideration of the phenomena that the toy theory fails to reproduce, notably, violations of Bell inequalities and the existence of a Kochen-Specker theorem, provides clues for how to proceed with this research program.

A version of this paper can be read here: http://www.arxiv.org/abs/quant-ph/0401052

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Quantum coherence: fact or fiction?
Stephen Bartlett (School of Physics, University of Sydney)

A controversy that has arisen surprisingly often in disparate fields of research is whether quantum coherences between eigenstates of a conserved quantity (such as charge or energy) are fact or fiction. I defend the idea that the resolution of the debate is to  recognize that there are two alternative but equally good paradigms of description; coherences are present when reference frames are treated classically, and are absent when reference frames are treated quantum mechanically. This suggests that many, if not all, superselection rules can be circumvented in principle, and that quantum states describe relations rather than intrinsic properties.

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The meeting will be held in the McRae Room (S418), Main Quadrangle (A14), University of Sydney.


Registration is free, but to assist with catering, please RSVP by email to Brad Weslake by Tuesday 12 April. Email: brad.weslake @ arts.usyd.edu.au (remove the spaces).


Last updated: 8 April 2005