The rapid increase in accuracy and stability of optical atomic clocks compared to the caesium atomic clock as the primary standard of time and frequency asks for a future redefinition of the second in the International System of Units (SI). The status of the optical clocks based on either single ions in radio-frequency traps or on neutral atoms stored in an optical lattice is described, with special emphasis on the current work at the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany). Besides the development and operation of different optical clocks with estimated fractional uncertainties in the range, the supporting work on ultra-stable lasers as core elements and the means to compare remote optical clocks with transportable standards, optical fibres, or frequency ratios is reported. Finally, the conditions, methods and next steps are discussed, which are the prerequisites for a future redefinition of the second.
L'amélioration rapide en termes de précision et de stabilité des horloges atomiques optiques par rapport à l'horloge atomique au césium, qui constitue la référence primaire pour le temps et la fréquence, appelle une future redéfinition de la seconde dans le système international d'unités (SI). L'état d'avancement des horloges optiques basées sur des ions uniques dans des pièges radiofréquence ou sur des atomes neutres confinés dans le réseau optique est décrit, en insistant particulièrement sur le travail en cours à la Physikalisch-Technische Bundesanstalt (PTB, Brunswick, Allemagne). À côté du développement et de la mise en œuvre de différentes horloges optiques avec des incertitudes fractionnelles estimées d'un ordre de grandeur de , les travaux sous-jacents sur les lasers ultra-stables comme éléments centraux ainsi que les moyens de comparer les horloges optiques lointaines avec des étalons transportables, des fibres optiques ou des rapports de fréquence sont exposés. Finalement, les conditions, les méthodes et les prochaines étapes sont discutées, qui sont des prérequis à une redéfinition de la seconde.
Mots-clés : Horloges optiques atomiques, Étalons de fréquence, Redéfinition future de la seconde, Diffusion des fréquences et des signaux horaires
Fritz Riehle 1
@article{CRPHYS_2015__16_5_506_0,
author = {Fritz Riehle},
title = {Towards a redefinition of the second based on optical atomic clocks},
journal = {Comptes Rendus. Physique},
pages = {506--515},
publisher = {Elsevier},
volume = {16},
number = {5},
year = {2015},
doi = {10.1016/j.crhy.2015.03.012},
language = {en},
}
Fritz Riehle. Towards a redefinition of the second based on optical atomic clocks. Comptes Rendus. Physique, The measurement of time / La mesure du temps, Volume 16 (2015) no. 5, pp. 506-515. doi : 10.1016/j.crhy.2015.03.012. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2015.03.012/
[1] http://www.bipm.org/en/publications/si-brochure/second.html
[2] Optical atomic clocks, Riv. Nuovo Cimento, Volume 36 (2013) no. 12, pp. 555-624 | DOI
[3] Optical atomic clocks, 13 Jul 2014 Rev. Mod. Phys. (accepted) | arXiv
[4] When should we change the definition of the second?, Philos. Trans. R. Soc. Lond. Ser. A, Math. Phys. Sci., Volume 369 (2011), pp. 4109-4130 | DOI
[5] On secondary representations of the second, Braunschweig (2006), pp. 282-288 www.eftf.org/proceedings/proceedingsEFTF2006.pdf (ISBN: 978-1-4673-2642-1)
[6] http://www.bipm.org/en/committees/cipm/publications-cipm.html#pv
[7] http://www.bipm.org/en/publications/mises-en-pratique/standard-frequencies.html
[8] Linear Paul trap design for an optical clock with Coulomb crystals, Appl. Phys. B, Volume 107 (2012), pp. 891-906 | DOI
[9] Frequency comparison of two high-accuracy Al+ optical clocks, Phys. Rev. Lett., Volume 104 (2010), p. 070802 | DOI
[10] Precision calculation of blackbody radiation shifts for optical frequency metrology, Phys. Rev. Lett., Volume 107 (2011), p. 143006 | DOI
[11] Wolfgang Paul – Nobel lecture: Electromagnetic traps for charged and neutral particles. Nobelprize.org. Nobel Media AB 2014. Web. 1 Dec 2014. www.nobelprize.org/nobel_prizes/physics/laureates/1989/paul-lecture.html.
[12] Novel miniature ion traps, Opt. Commun., Volume 101 (1993), pp. 32-36 | DOI
[13] Ionic crystals in a linear Paul trap, Phys. Rev. A, Volume 45 (1992), pp. 6493-6501 | DOI
[14] Frequency measurement of the optical clock transition of 40Ca+ ions with an uncertainty of level, Appl. Phys. Express, Volume 1 (2008), p. 067011 | DOI
[15] Absolute frequency measurement of the 40Ca+ 4s 2S1/2–3d 2D5/2 clock transition, Phys. Rev. Lett., Volume 102 (2009), p. 023002 | DOI
[16] Hertz-level measurement of the 40Ca+ 4s 2S1/2–3d 2D5/2 clock transition frequency with respect to the SI second through the Global Positioning System, Phys. Rev. A, Volume 85 (2012), p. 030503(R) | DOI
[17] Hertz-level measurement of the optical clock frequency in a single 88Sr+ ion, Science, Volume 306 (2004), pp. 1355-1358 | DOI
[18] 88Sr+ 445-THz single ion reference at the level via control and cancellation of systematic uncertainties and its measurement against the SI second, Phys. Rev. Lett., Volume 109 (2012), p. 203002 | DOI
[19] Frequency ratio of Al+ and Hg+ single-ion optical clocks, metrology at the 17th decimal place, Science, Volume 319 (2008), pp. 1808-1812 | DOI
[20] Frequency ratio of two optical clock transitions in 171Yb+ and constraints on the time-variation of fundamental constants, Phys. Rev. Lett., Volume 113 (2014), p. 210801 | DOI
[21] Improved limit on a temporal variation of from comparisons of Yb+ and Cs atomic clocks, Phys. Rev. Lett., Volume 113 (2014), p. 210802 | DOI
[22] A Cs-based optical frequency measurement using cross-linked optical and microwave oscillators, Phys. Rev. A, Volume 89 (2014), p. 023820 | DOI
[23] Hyper-Ramsey spectroscopy of optical clock transitions, Phys. Rev. A, Volume 81 (2010), p. 011804(R) | DOI
[24] High-accuracy optical clock based on the octupole transition in 171Yb+, Phys. Rev. Lett., Volume 108 (2012), p. 090801 | DOI
[25] Sympathetic cooling of mixed-species two-ion crystals for precision spectroscopy, Phys. Rev. A, Volume 85 (2012), p. 043412 | DOI
[26] Ultrastable optical clock with neutral atoms in an engineered light shift trap, Phys. Rev. Lett., Volume 91 (2003) (173005–1–4) | DOI
[27] Cryogenic optical lattice clocks, Nature Photon., Volume 9 (2015), pp. 185-189 | DOI
[28] An optical lattice clock with accuracy and stability at the level, Nature, Volume 506 (2014), pp. 71-75 | DOI
[29] Experimental realisation of an optical second with strontium lattice clocks, Nat. Commun., Volume 4 (2013), p. 2109 | DOI
[30] A strontium lattice clock with inaccuracy and its frequency, New J. Phys., Volume 16 (2014), p. 073023 | DOI
[31] Spectroscopy and frequency measurement of the 87Sr clock transition by laser linewidth transfer using an optical frequency comb, Appl. Phys. Express, Volume 7 (2014), p. 012401 | DOI
[32] Direct comparison of distant optical lattice clocks at the uncertainty, Appl. Phys. Express, Volume 4 (2011) no. 8, p. 082203 | DOI
[33] The 87Sr optical frequency standard at PTB, Metrologia, Volume 48 (2011), pp. 399-407 | DOI
[34] High accuracy correction of blackbody radiation shift in an optical lattice clock, Phys. Rev. Lett., Volume 109 (2012), p. 263004 | DOI
[35] 87Sr lattice clock with inaccuracy below , Phys. Rev. Lett., Volume 98 (2007), p. 083002 | DOI
[36] An optical lattice clock with spin-polarized 87Sr atoms, Eur. Phys. J. D, Volume 48 (2008), pp. 11-17 | DOI
[37] The absolute frequency of the 87Sr optical clock transition, Metrologia, Volume 45 (2008), pp. 539-548 | DOI
[38] Measuring the frequency of a Sr optical lattice clock using a 120 km coherent optical transfer, Opt. Lett., Volume 34 (2009), pp. 692-694 | DOI
[39] Stability transfer between two clock lasers operating at different wavelengths for absolute frequency measurement of clock transition in 87Sr, Appl. Phys. Express, Volume 5 (2012), p. 022701 | DOI
[40] Direct comparison of a Ca+ single-ion clock against a Sr lattice clock to verify the absolute frequency measurement, Opt. Express, Volume 20 (2012), p. 022034 | DOI
[41] http://www.bipm.org/en/publications/mises-en-pratique/standard-frequencies.html
[42] A 920-kilometer optical fibre link for frequency metrology at the 19th decimal place, Science, Volume 336 (2012) no. 6080, pp. 441-444 | DOI
[43] N. Poli, M. Schioppo, S. Vogt, S. Falke, U. Sterr, C. Lisdat, G.M. Tino, A transportable strontium optical lattice clock, Appl. Phys. B online, . | DOI
[44] et al. Development of a strontium optical lattice clock for the SOC mission on the ISS, C. R. Physique, Volume 16 (2015) ( this issue ) | DOI
[45] S. Vogt, to be published (2015).
[46] Laser phase and frequency stabilisation using an optical resonator, Appl. Phys. B, Volume 31 (1983), pp. 97-105 | DOI
[47] Spectrally narrow, long-term stable optical frequency reference based on a Eu3+:Y2SiO5 crystal at cryogenic temperature, Phys. Rev. Lett., Volume 107 (2011), p. 223202 | DOI
[48] Absolute and relative stability of an optical frequency reference based on spectral hole burning in Eu3+:Y2SiO5, Phys. Rev. Lett., Volume 111 (2013), p. 237402 | DOI
[49] Shifts of optical frequency references based on spectral-hole burning in Eu3+:Y2SiO5, New J. Phys., Volume 15 (2013), p. 033006 | DOI
[50] Prospects for a millihertz-linewidth laser, Phys. Rev. Lett., Volume 102 (2009), p. 163601 | DOI
[51] A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity, Nature Photon., Volume 6 (2012), pp. 687-692 | DOI
[52] Ultrastable lasers based on vibration insensitive cavities, Phys. Rev. A, Volume 79 (2009), p. 053829 | DOI
[53] Providing short-term stability of a 1.5 μm laser to optical clocks, IEEE Trans. Instrum. Meas., Volume 62 (2013) no. 6, pp. 1556-1562 | DOI
[54] S. Häfner, S. Falke, C. Grebing, S. Vogt, T. Legero, M. Merimaa, C. Lisdat, U. Sterr, fractional laser frequency instability with a long room-temperature cavity, Opt. Lett. (submitted).
[55] Time and frequency comparisons using radiofrequency signals from satellites, C. R. Physique, Volume 16 (2015) ( this issue ) | DOI
[56] Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km, Opt. Lett., Volume 39 (2014), pp. 4072-4075 | DOI
[57] Atomic clock ensemble in space, J. Phys. Conf. Ser., Volume 327 (2011) no. 1, p. 012049 | DOI
[58] Time transfer by laser link (T2L2): characterization and calibration of the flight instrument, Metrologia, Volume 51 (2014), pp. 503-515
[59] An atomic clock with instability, Science, Volume 341 (2013), pp. 1215-1218 | DOI
[60] Optical clocks and relativity, Science, Volume 329 (2010), pp. 1630-1633 | DOI
[61] On a relativistic geodesy, Bull. Géod., Volume 59 (1985), pp. 207-220 | DOI
[62] http://www.bipm.org/en/measurement-units/new-si/
[63] Comparing high accuracy frequency standards via TAI, Braunschweig (2006), pp. 476-485 www.eftf.org/proceedings/proceedingsEFTF2006.pdf (ISBN: 978-1-4673-2642-1)
[64] Nuclear clocks based on resonant excitation of γ-transitions, C. R. Physique, Volume 16 (2015) ( this issue ) | DOI
[65] Nuclear laser spectroscopy of the 3.5 eV transition in Th-229, Europhys. Lett., Volume 61 (2003), pp. 181-186 | DOI
[66] Excitation of the isomeric 229mTh nuclear state via an electronic bridge process in 229Th+, Phys. Rev. Lett., Volume 105 (2010), p. 182501 (4 p.) | DOI
[67] http://www.euramet.org/fileadmin/docs/Publications/roadmaps/TC_TF_Roadmaps_2012_chart.pdf
Cited by Sources:
Comments - Policy