Critical exponents for an impurity in a bosonic Josephson junction: Position measurement as a phase transition
Abstract
We use fidelity susceptibility to calculate quantum critical scaling exponents for a system consisting of N identical bosons interacting with a single impurity atom in a doublewell potential (bosonic Josephson junction). Above a critical value of the bosonimpurity interaction energy there is a spontaneous breaking of Z_{2} symmetry corresponding to a secondorder quantum phase transition from a balanced to an imbalanced number of particles in either the left or the righthand well. We show that the exponents match those in the LipkinMeshkovGlick 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.
 Publication:

Physical Review A
 Pub Date:
 December 2014
 DOI:
 10.1103/PhysRevA.90.063617
 arXiv:
 arXiv:1410.0077
 Bibcode:
 2014PhRvA..90f3617M
 Keywords:

 03.75.Lm;
 03.65.Ta;
 67.85.Pq;
 05.30.Rt;
 Tunneling Josephson effect BoseEinstein condensates in periodic potentials solitons vortices and topological excitations;
 Foundations of quantum mechanics;
 measurement theory;
 Mixtures of Bose and Fermi gases;
 Condensed Matter  Quantum Gases
 EPrint:
 9 pages, 5 figures