Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Phys Rev Lett. 2009 Oct 2;103(14):140501. doi: 10.1103/PhysRevLett.103.140501. Epub 2009 Sep 29.
Quantum phase transitions occur at zero temperature, when the ground state of a Hamiltonian undergoes a qualitative change as a function of a control parameter. We consider a particularly interesting system with competing one-, two-, and three-body interactions. Depending on the relative strength of these interactions, the ground state of the system can be a product state, or it can exhibit genuine tripartite entanglement. We experimentally simulate such a system in a NMR quantum simulator and observe the different ground states. By adiabatically changing the strength of one coupling constant, we push the system from one ground state to a qualitatively different ground state. We show that these ground states can be distinguished and the transitions between them observed by measuring correlations between the spins or the expectation values of suitable entanglement witnesses.
量子相变发生在零温度下，当哈密顿量的基态随着控制参数的变化而发生定性变化时。我们考虑一个特别有趣的系统，其中存在竞争的单、双和三体相互作用。根据这些相互作用的相对强度，系统的基态可以是乘积态，也可以表现出真正的三分纠缠。我们在 NMR 量子模拟器中实验模拟了这样一个系统，并观察到了不同的基态。通过绝热地改变一个耦合常数的强度，我们将系统从一个基态推到一个定性上不同的基态。我们表明，可以通过测量自旋之间的相关性或合适的纠缠见证者的期望值来区分这些基态，并观察它们之间的转变。
