Direct observation of quantum criticality in Ising spin chains
  We use NMR quantum simulators to study antiferromagnetic Ising spin chains undergoing quantum phase transitions. Taking advantage of the sensitivity of the systems near criticality, we detect the critical points of the transitions using a direct measurement of the Loschmidt echo. We test our simulators for spin chains of even and odd numbers of spins, and compare the experimental results to theoretical predictions. 
Jingfu Zhang, Fernando M. Cucchietti, C. M. Chandrashekar, Martin   Laforest, Colm A. Ryan, Michael Ditty, Adam Hubbard, Joh...