Nuclear Magnetic Resonance Implementation of a Quantum Clock   Synchronization Algorithm
  The quantum clock synchronization algorithm proposed by I. L. Chuang (Phys. Rev. Lett, 85, 2006(2000)) has been implemented in a three qubit nuclear magnetic resonance quantum system. The effective-pure state is prepared by the spatial averaging approach. The time difference between two separated clocks can be determined by reading out directly through the NMR spectra. 
Jingfu Zhang, Guilu Long, Zhiwei Deng, Wenzhang Liu, and Zhiheng Lu