Suter, DieterZhang, JingfuPeng, XinhuaRajendran, Nageswaran2008-06-022008-06-022008-03-13Zhang, Jingfu; Peng, Xinhua; Rajendran, Nageswaran; Suter, Dieter: Detection of Quantum Critical Points by a Probe Qubit. In: Physical Review Letters Jg. 100(2008), 100501.http://hdl.handle.net/2003/25408http://dx.doi.org/10.17877/DE290R-2907Quantum 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.en©2008 The American Physical Society530Text10.1103/PhysRevLett.100.100501http://dx.doi.org/10.1103/PhysRevLett.100.100501