paper

Critical exponents for an impurity in a bosonic Josephson junction: Position measurement as a phase transition

arXiv:1410.0077 · doi:10.1103/PhysRevA.90.063617

Abstract

We use fidelity susceptibility to calculate quantum critical scaling exponents for a system consisting of identical bosons interacting with a single impurity atom in a double well potential (bosonic Josephson junction). Above a critical value of the boson-impurity interaction energy there is a spontaneous breaking of symmetry corresponding to a second order quantum phase transition from a balanced to an imbalanced number of particles in either the left or right hand well. We show that the exponents match those in the Lipkin-Meshkov-Glick and Dicke models suggesting that the impurity model is in the same universality class. The phase transition can be interpreted as a measurement of the position of the impurity by the bosons.

9 pages, 5 figures

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