Quantum Clock Synchronization Based on Shared Prior Entanglement
  We demonstrate that two spatially separated parties (Alice and Bob) can utilize shared prior quantum entanglement, and classical communications, to establish a synchronized pair of atomic clocks. In contrast to classical synchronization schemes, the accuracy of our protocol is independent of Alice or Bob's knowledge of their relative locations or of the properties of the intervening medium. 
Richard Jozsa, Daniel S. Abrams, Jonathan P. Dowling, and Colin P.   Williams