A Quantum Network of Clocks
The concept of world-wide quantum clock network: Illustration of a cooperative clock operation protocol in which individual parties (for example, satellite-based atomic clocks from different countries) jointly allocate their respective resources in a global network involving entangled quantum states. This guarantees an optimal use of the global resources, achieving an ultra-precise clock signal limited only by the fundamental bounds of quantum metrology and, in addition, guaranteeing secure distribution of the clock signal. b. [Figure reprinted by permission from Macmillan Publishers Ltd: P. Kómár, E. M. Kessler, M. Bishof, L. Jiang, A. S. Sørensen, J. Ye & M. D. Lukin, "A quantum network of clocks," Nature Physics 10 (2014) doi:10.1038/nphys3000 ©2014.]
A quantum network of atomic clocks could create even more accurate and stable time-keeping devices than present atomic clocks, reports a paper published online this week in Nature Physics. Such a network could have technological applications as well as provide a resource for Earth science studies and fundamental tests of relativity and quantum gravity.
The modern world relies heavily on accurate time-keeping, for instance for the operation of the Global Positioning System, or synchronization in high-frequency financial trading. Based on a combination of precision metrology and quantum technologies, Harvard physics graduate student Peter Kómár, postdoc Eric Kessler, Prof. Mikhail Lukin, and colleagues from University of Colorado, Yale, and Niels Bohr Institute, Denmark, show that a network of atomic clocks sharing quantum entanglement would achieve a time-keeping stability better than that of any individual clock. Distributed around the Earth and on satellites, the clock network could maintain and synchronize time standards across multiple parties in real-time — a true world clock. Furthermore, by its very nature, this quantum network of atomic clocks would be protected against quantum-cryptographic attacks.