Optimized multiparty quantum clock synchronization
Radel Ben-Av, Iaakov Exman · Physical Review A · 2011
A multiparty protocol for distributed quantum clock synchronization has been claimed to provide universal limits on the clock accuracy, viz., that accuracy monotonically decreases with the number $n$ of party members. But this is only true for synchronization when one limits oneself to $W$ states. This work shows that the usage of Z (Symmetric Dicke) states, a generalization of $W$ states, results in improved accuracy, having a maximum when $\ensuremath{\lfloor}n/2\ensuremath{\rfloor}$ of its members have their qubits with a $|1\ensuremath{\rangle}$ eigenstate.