1303.3437 (Yong-Liang Zhang et al.)

Criterion on remote clocks synchronization within a Heisenberg scaling
accuracy    [PDF]

Yong-Liang Zhang, Yu-Ran Zhang, Liang-Zhu Mu, Heng Fan

We propose a quantum method to judge whether two spatially separated clocks have been synchronized within a specific accuracy $\sigma$. If the measurement result of the experiment is obviously a nonzero value, the time difference between two clocks is smaller than $\sigma$; otherwise the difference is beyond $\sigma$. On sharing the 2$N$-qubit bipartite maximally entangled state in this scheme, the accuracy of judgement can be enhanced to $\sigma\sim{\pi}/{(\omega(N+1))}$. This criterion is consistent with Heisenberg scaling that can be considered as beating standard quantum limit, moreover, the unbiased estimation condition is not necessary.

View original: http://arxiv.org/abs/1303.3437