Geopotential measurements with synchronously linked optical lattice clocks
By T. Takano, Masao Takamoto, Ichiro Ushijima, N. Ohmae, T. Akatsuka, A. Yamaguchi, Y. Kuroishi, H. Munekane, B. Miyahara, Hidetoshi Katori. Nature Photonics, 2016
216 citations recorded by the source corpus.
Real-time geopotential measurements with two synchronously linked optical lattice clocks are demonstrated. A height difference between the two clocks separated by 15 km is determined, with an uncertainty of 5 cm, by means of a gravitational redshift. According to Einstein's theory of relativity, the passage of time changes in a gravitational field1,2. On Earth, raising a clock by 1 cm increases its apparent tick rate by 1.1 parts in 1018, allowing chronometric levelling3 through comparison of optical clocks1,4,5. Here, we demonstrate such geopotential measurements by determining the height difference of master and slave clocks separated by 15 km with an uncertainty of 5 cm. A subharmonic of the master clock laser is delivered through a telecom fibre6 to synchronously operate7 the distant clocks. Clocks operated under such phase coherence reject clock laser noise and facilitate proposals for linking clocks8,9 and interferometers10. Taken over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be 1,652.9(5.9) × 10−18, consistent with an independent measurement by levelling and gravimetry11. Our system demonstrates a building block for an internet of clocks, which may constitute ‘quantum benchmarks’, serving as height references with dynamic responses.
Subfields: Atomic and Molecular Physics, and Optics, Surgery
View Paper: https://www.semanticscholar.org/paper/02b8265d1276cd0ebb6a1de15880af27dc405b16
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In Atomic and Molecular Physics, and Optics
Citations in the corpus
- The CIPM list of recommended frequency standard values: guidelines and procedures (2018, background): “In the meantime, optical atomic clocks, optical long haul links and the various methods of all-optical frequency metrology are finding widespread applications and have even led to the creation of novel fields like relativistic geodesy [96, 97].”
- Micius quantum experiments in space (2022, background): “They cover the fields of time and frequency metrology [comparison of distant clocks (Takano et al., 2016)], quantum communications [synchronization of quantum phases for wide areas (Lucamarini et al.”