We extend the single source approach of Valencia et al in order to synchronize the clocks of an N user start network, connected both through fiber and in free space. Entangled photon pairs from a centralized SPDC source are distributed through a 1 by N splitter to four remote users arranged in a star topology. Using commercially available single photon detectors and time taggers, we achieve median time precision of 50 ps for atomic oscillators and 20 ps for GPS displayed oscillators in our Kalman models. Thus, we achieve three order of magnitude improvement over GPS alone. By monitoring the drift fo the correlation peaks over time, we also extract the frequency skew between users's local clocks to 35ps/s precision. From these measurements, e3ach user can compute its offset and drift relative to every other user, achieving full network synchronization without a central clock.

翻译：我们扩展了Valencia等人提出的单源方法，以实现通过光纤和自由空间连接的N用户星型网络的时钟同步。来自中心化SPDC源的纠缠光子对通过1×N分束器分配给以星型拓扑排列的四个远程用户。使用商用单光子探测器和时间标记器，我们的卡尔曼模型实现了原子振荡器50 ps的中值时间精度和GPS显示振荡器20 ps的中值时间精度。因此，我们实现了相对于单独使用GPS三个数量级的性能提升。通过监测相关峰值随时间的漂移，我们还以35 ps/s的精度提取了用户本地时钟之间的频率偏差。基于这些测量，每个用户可以计算其相对于其他每个用户的偏移和漂移，从而在没有中心时钟的情况下实现完整的网络同步。