A quantum network of clocks


The development of precise atomic clocks plays an increasingly important role in modern society. Shared timing information constitutes a key resource for navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System. By combining precision metrology and quantum networks, we propose a quantum, cooperative protocol for operating a network of geographically remote optical atomic clocks. Using nonlocal entangled states, we demonstrate an optimal utilization of global resources, and show that such a network can be operated near the fundamental precision limit set by quantum theory. Furthermore, the internal structure of the network, combined with quantum communication techniques, guarantees security both from internal and external threats. Realization of such a global quantum network of clocks may allow construction of a real-time single international time scale (world clock) with unprecedented stability and accuracy.

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Figure 1: The concept of world-wide quantum clock network.
Figure 2: Entangled state preparation between distant nodes.
Figure 3: Performance of different operation schemes. Comparison of the achievable (rescaled) Allan deviation using clock networks of different types and degrees of cooperation.
Figure 4: Schematics of security countermeasures.


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We are grateful to T. Rosenband, V. Vuletić, J. Borregaard and T. Nicholson for enlightening discussions. This work was supported by NSF, CUA, ITAMP, HQOC, JILA PFC, NIST, DARPA QuASAR and Quiness programs, the Alfred P. Sloan Foundation, the Packard Foundation, ARO MURI, and the ERC grant QIOS (grant no. 306576); M.B. acknowledges support from NDSEG and NSF GRFP. It is dedicated to R. Blatt and P. Zoller on the occasion of their 60th birthday, when initial ideas for this work were formed.

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All authors contributed extensively to the work presented in this paper.

Correspondence to M. D. Lukin.

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The authors declare no competing financial interests.

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Kómár, P., Kessler, E., Bishof, M. et al. A quantum network of clocks. Nature Phys 10, 582–587 (2014). https://doi.org/10.1038/nphys3000

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