将来の超高精度タイミングを利用した静止衛星リンクの基礎を築く(NIST Lays Groundwork for Future Ultra-Precise Timing Links to Geosynchronous Satellites)

2023-06-21 米国国立標準技術研究所(NIST)

＜関連情報＞

• https://www.nist.gov/news-events/news/2023/06/nist-lays-groundwork-future-ultra-precise-timing-links-geosynchronous
• https://www.nature.com/articles/s41586-023-06032-5
• https://www.nature.com/articles/s41586-022-05225-8

将来の静止衛星リンクのための量子限界光時間転送 Quantum-limited optical time transfer for future geosynchronous links

Emily D. Caldwell,Jean-Daniel Deschenes,Jennifer Ellis,William C. Swann,Benjamin K. Stuhl,Hugo Bergeron,Nathan R. Newbury & Laura C. Sinclair
Nature  Published:21 June 2023
DOI:https://doi.org/10.1038/s41586-023-06032-5

Abstract

The combination of optical time transfer and optical clocks opens up the possibility of large-scale free-space networks that connect both ground-based optical clocks and future space-based optical clocks. Such networks promise better tests of general relativity^1,2,3, dark-matter searches⁴ and gravitational-wave detection⁵. The ability to connect optical clocks to a distant satellite could enable space-based very long baseline interferometry^6,7, advanced satellite navigation⁸, clock-based geodesy^2,9,10 and thousandfold improvements in intercontinental time dissemination^11,12. Thus far, only optical clocks have pushed towards quantum-limited performance¹³. By contrast, optical time transfer has not operated at the analogous quantum limit set by the number of received photons. Here we demonstrate time transfer with near quantum-limited acquisition and timing at 10,000 times lower received power than previous approaches^{14,15,16,17,18,19,20,21,22,23,24}. Over 300 km between mountaintops in Hawaii with launched powers as low as 40 µW, distant sites are synchronized to 320 attoseconds. This nearly quantum-limited operation is critical for long-distance free-space links in which photons are few and amplification costly: at 4.0 mW transmit power, this approach can support 102 dB link loss, more than sufficient for future time transfer to geosynchronous orbits.

時間プログラマブル周波数コムと量子限定測距におけるその利用 The time-programmable frequency comb and its use in quantum-limited ranging

Emily D. Caldwell,Laura C. Sinclair,Nathan R. Newbury & Jean-Daniel Deschenes
Nature  Published:05 October 2022
DOI:https://doi.org/10.1038/s41586-022-05225-8

Abstract

Two decades after its invention, the classic self-referenced frequency comb laser is an unrivalled ruler for frequency, time and distance metrology owing to the rigid spacing of its optical output^1,2. As a consequence, it is now used in numerous sensing applications that require a combination of high bandwidth and high precision^3,4,5. Many of these applications, however, are limited by the trade-offs inherent in the rigidity of the comb output and operate far from quantum-limited sensitivity. Here we demonstrate an agile programmable frequency comb where the pulse time and phase are digitally controlled with ±2-attosecond accuracy. This agility enables quantum-limited sensitivity in sensing applications as the programmable comb can be configured to coherently track weak returning pulse trains at the shot-noise limit. To highlight its capabilities, we use this programmable comb in a ranging system, reducing the required power to reach a given precision by about 5,000-fold compared with a conventional dual-comb system. This enables ranging at a mean photon per pulse number of 1/77 while retaining the full accuracy and precision of a rigid frequency comb. Beyond ranging and imaging^{6,7,8,9,10,11,12}, applications in time and frequency metrology^{1,2,5,13,14,15,16,17,18,19,20,21,22,23}, comb-based spectroscopy^{24,25,26,27,28,29,30,31,32}, pump–probe experiments³³ and compressive sensing^34,35 should benefit from coherent control of the comb-pulse time and phase.