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Résumé |
Several notions from quantum information theory have been recently
imported to the condensed matter field.
Amongst them, entanglement entropy and fidelity are of particular
interest as they can directly detect quantum phase transitions,
without any physical input. Unfortunately, these quantities are
difficult to compute even for standard spin models.
In this talk, I will show how the valence bond basis, which sounds
like old-school quantum mechanics, can give an insight on these new
problems. After a short introduction to the properties of the valence-
bond basis, I will present some recent works on how to compute
entanglement entropy and fidelity using this approach. This will be
illustrated on quantum phase transitions in the Heisenberg model on 2d
lattices.
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