paper

Quantum criticality as a resource for quantum estimation

arXiv:0708.1089 · doi:10.1103/PhysRevA.78.042105

Abstract

We address quantum critical systems as a resource in quantum estimation and derive the ultimate quantum limits to the precision of any estimator of the coupling parameters. In particular, if L denotes the size of a system and λis the relevant coupling parameters driving a quantum phase transition, we show that a precision improvement of order 1/L may be achieved in the estimation of λat the critical point compared to the non-critical case. We show that analogue results hold for temperature estimation in classical phase transitions. Results are illustrated by means of a specific example involving a fermion tight-binding model with pair creation (BCS model).

7 pages. Revised and extended version. Gained one author and a specific example

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