Probing Quantum Phase Transitions on a Spin Chain with a Double Quantum   Dot
  Quantum phase transitions (QPTs) in qubit systems are known to produce singularities in the entanglement, which could in turn be used to probe the QPT. Current proposals to measure the entanglement are challenging however, because of their nonlocal nature. Here we show that a double quantum dot coupled locally to a spin chain provides an alternative and efficient probe of QPTs. We propose an experiment to observe a QPT in a triple dot, based on the well-known singlet projection technique. 
Yun-Pil Shim, Sangchul Oh, Jianjia Fei, Xuedong Hu, Mark Friesen
cond-mat.mes-hall quant-ph