Talk by Adam Caulton at the MCMP (Wed. 15.05)

[Karim Thebault]

Speaker: Adam Caulton (Cambridge)
Wednesday 15th May 2013
Ludwigstr.31 Room E021
Time: 4 to 6 pm

Title: Individuating so-called "indistinguishable" quantum systems

Abstract: In this talk I investigate and build on recent heterodox
proposals by Zanardi and others about the idea of a natural decomposition
of an assembly. I argue that so-called "indistinguishable" quantum systems
may, in fact, be individuated---that is, picked out uniquely by some
(permutation-invariant) description---and may in some cases be ascribed
non-trivial reduced density operators. This heterodox account has several
interesting consequences, that I will outline.  First, it entails that the
received opinion within the quantum philosophy literature, that bosons and
fermions are always indiscernible, at least by their monadic properties (a
view shared even by Muller, Saunders and Seevinck), is mistaken.  Second,
the account prompts a revision of the notion of entanglement in cases where
permutation-invariance is imposed.  More specifically: non-separability of
the joint state is no longer sufficient for that state's being entangled.
 This revision happily coincides with recent proposals by Ghirardi,
Marinatto and Weber.  Third, arbitrariness in the individuating description
suggests that a quantum analogue of David Lewis's counterpart theory is an
appropriate metaphysics for such systems.
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