title: Detection of quantum critical points by a probe qubit.
abstract: Quantum phase transitions occur when the ground state of a quantum system undergoes a qualitative change when an external control parameter reaches a critical value. Here, we demonstrate a technique for studying quantum systems undergoing a phase transition by coupling the system to a probe qubit. It uses directly the increased sensibility of the quantum system to perturbations when it is close to a critical point. Using an NMR quantum simulator, we demonstrate this measurement technique for two different types of quantum phase transitions in an Ising spin chain.
authors: Technische Universität Dortmund, 44221 Dortmund, Germany. zhangjfu2000@yahoo.com
authors: Jingfu
authors: J
authors: Zhang
authors: Xinhua
authors: X
authors: Peng
authors: Nageswaran
authors: N
authors: Rajendran
authors: Dieter
authors: D
authors: Suter