ANALYSIS AND DATA PROCESSING SYSTEMS

A scheme for measuring the gravitational frequency shift of hydrogen clocks during their movement between two points located at different orthometric altidudes with simultaneous signal transmission via radio and fiber-optic communication lines has been implemented.

Practical interest in studying the gravitational frequency shift of quantum standards is associated with the need to take it into account to improve accuracy in navigation satellite systems. Such measurements were performed using a space synchronization channel using signals from global navigation satellite systems. This became especially relevant when improving the metrological characteristics of quantum frequency and time standards, in particular, using transportable clocks based on optical lattices when transmitting a signal via fiber-optic communication lines. On the other hand, using quantum clocks, measurements of the difference in orthometric heights are performed using the relativistic synchronization method and the simultaneous use of the frequency standard redshift effect due to time dilation in a gravitational field and the redshift effect of photons overcoming the gravitational field.

This paper presents the results of measuring the gravitational frequency shift of a hydrogen clock when it is moved between two points located at different orthometric heights with signal transmission via a fiber-optic communication line and via a radio channel. In the first case, the radiation of a diode laser at a wavelength of 1.5 μm amplitude-modulated by a signal from the transported hydrogen clock at a frequency of 10 MHz, was transmitted via a fiber-optic communication line when a stationary hydrogen clock was used as a reference. Transmission via a radio channel was carried out via a coaxial radio frequency cable. The measurements were carried out on the territory of the West Siberian branch of the FSUE "VNIIFTRI".

1. Pound R.V., Rebka Jr. G.A. Gravitational red-shift in nuclear resonance. Physical Review Letters, 1959, vol. 3 (9), pp. 439–441.

2. Pound R.V., Rebka Jr. G.A. Apparent weight of photons. Physical Review Letters, 1960, vol. 4 (7), pp. 337–341.

3. Pound R.V., Snider J.L. Effect of gravity on nuclear resonance. Physical Review Letters, 1964, vol. 13 (18), pp. 539–540.

4. Ashby N. Relativity in the global positioning system. Living Reviews in Relativity, 2003, vol. 6, art. 1, pp. 1–42. DOI: 10.12942/lrr-2003-1.

5. Takamoto M., Ushijima I., Ohmae N., Yahagi T., Kokado K., Shinkai H., Katori H. Test of general relativity by a pair of transportable optical lattice clocks. Nature Photonics, 2020, vol. 14 (7), pp. 411–415. DOI: 10.1038/s41566-020-0619-8.

6. Takano T., Takamoto M., Ushijima I., Ohmae N., Akatsuka T., Yamaguchi A., Kuroishi Y., Munekane H., Miyahara B., Katori H. Real-time geopotentiometry with synchronously linked optical lattice clocks. ArXiv preprint. Available at: https://arxiv.org/pdf/1608.07650 (accessed 28.11.2024).

7. Ye J., Peng J.-L Jones R.J., Holman K.W., Hall J.L., Jones D.J., Diddams S.A., Kitching J., Bize S., Bergquist J.C. Delivery of high-stability optical and microwave frequency standards over an optical fiber network. Journal of the Optical Society of America B, 2003, vol. 20 (7), pp. 1459–1467.

8. Takano T., Takamoto M., Ushijima I., Ohmae N., Akatsuka T., Yamaguchi A., Kuroishi Y., Munekane H., Miyahara B., Katori H. Geopotential measurements with synchronously linked optical lattice clocks. Nature Photonics, 2016, vol. 10, pp. 662–666. DOI: 10.1038/nphoton.2016.159.

9. Liu D., Wu L., Xiong Ch., Bao L. Geopotential difference measurement using two transportable optical clocks’ frequency comparisons. Remote Sensing, 2024, vol. 16, pp. 2462–2477.

10. Grotti J., Koller S., Vogt S., et al. Geodesy and metrology with a transportable optical clock. Nature Physics, 2018, vol. 14, pp. 437–441. DOI: 10.1038/s41567-017-0042-3.

11. Lisdat C., Grosche G., Quintin N., et al. A clock network for geodesy and fundamental science. Nature Communications, 2015, vol. 7, pp. 1038–1051. DOI: 10.1038/ncomms12443.

12. Calonico D., Bertacco E.K., Calosso C.E., Clivati C., Costanzo G.A., Frittelli M., Godone A., Mura A., Poli N., Sutyrin D.V., Tino G., Zucco M.E., Levi F. High-accuracy coherent optical frequency transfer over a doubled 642-km fiber link. Applied Physics B, 2014, vol. 117, pp. 979–986.

13. Fateev V.F., Rybakov E.A. Eksperimental'naya proverka kvantovogo nivelira na mobil'nykh kvantovykh chasakh [Experimental verification of a quantum level on a mobile quantum clock]. Doklady Rossiiskoi akademii nauk. Fizika, tekhnicheskie nauki = Doklady Physics, 2021, vol. 496, pp. 41–44. DOI: 10.31857/S2686740020060097. (In Russian).

14. Fateev V.F. Relyativistskaya teoriya i primenenie kvantovogo nivelira v seti «Kvantovyi futshtok» [Relativistic theory and application of the quantum level and the Quantum Footstock network]. Al'manakh sovremennoi metrologii = Al'manac of modern metrology, 2020, no. 3, pp. 11–52.

15. Voskoboynikov Yu.E. Chastotnaya model' sglazhivayushchego kubicheskogo splaina i ee kharakteristiki [Frequency model of a smoothing cubic spline and it’s characteristics]. Sovremennye naukoemkie tekhnologii = Modern High Technologies, 2022, no. 5-1, pp. 18–23.