[1] Hänsch T W. Nobel lecture: passion for precision[J]. Reviews of Modern Physics, 78, 1297-1309(2006).

[2] Sanner C, Huntemann N, Lange R et al. Optical clock comparison for Lorentz symmetry testing[J]. Nature, 567, 204-208(2019).

[3] Normile D, Clery D. First global telescope opens an eye on the cold universe[J]. Science, 333, 1820-1823(2011).

[4] Takano T, Takamoto M, Ushijima I et al. Geopotential measurements with synchronously linked optical lattice clocks[J]. Nature Photonics, 10, 662-666(2016).

[5] Kolkowitz S, Pikovski I, Langellier N et al. Gravitational wave detection with optical lattice atomic clocks[J]. Physical Review D, 94, 124043(2016).

[6] Wcisło P, Morzyński P, Bober M et al. Experimental constraint on dark matter detection with optical atomic clocks[J]. Nature Astronomy, 1, 0009(2017).

[7] Godun R M. Nisbet-Jones P B R, Jones J M, et al. Frequency ratio of two optical clock transitions in 171Yb + and constraints on the time variation of fundamental constants[J]. Physical Review Letters, 113, 210801(2014).

[8] Dow J M, Neilan R E, Rizos C. The international GNSS service in a changing landscape of global navigation satellite systems[J]. Journal of Geodesy, 83, 191-198(2009).

[9] Weyers S, Gerginov V, Kazda M et al. Advances in the accuracy, stability, and reliability of the PTB primary fountain clocks[J]. Metrologia, 55, 789-805(2018).

[11] Brewer S M, Chen J S, Hankin A M et al. 27Al + quantum-logic clock with a systematic uncertainty below 10 -18[J]. Physical Review Letters, 123, 033201(2019).

[12] Huntemann N, Sanner C, Lipphardt B et al. Single-ion atomic clock with 3×10 -18 systematic uncertainty[J]. Physical Review Letters, 116, 063001(2016).

[13] McGrew W F, Zhang X, Fasano R J et al. Atomic clock performance enabling geodesy below the centimetre level[J]. Nature, 564, 87-90(2018).

[14] Bothwell T, Kedar D, Oelker E et al. JILA SrI optical lattice clock with uncertainty of 2.0×10 -18[J]. Metrologia, 56, 065004(2019).

[15] Riehle F, Gill P, Arias F et al. The CIPM list of recommended frequency standard values: guidelines and procedures[J]. Metrologia, 55, 188-200(2018).

[16] Chou C W, Hume D B, Koelemeij J C et al. Frequency comparison of two high-accuracy Al + optical clocks[J]. Physical Review Letters, 104, 070802(2010).

[17] Wineland D J, Monroe C, Itano W M et al. Experimental issues in coherent quantum-state manipulation of trapped atomic ions[J]. Journal of Research of the National Institute of Standards and Technology, 103, 259-328(1998).

[18] Herschbach N, Pyka K, Keller J et al. Linear Paul trap design for an optical clock with Coulomb crystals[J]. Applied Physics B, 107, 891-906(2012).

[19] Aharon N, Spethmann N, Leroux I D et al. Robust optical clock transitions in trapped ions using dynamical decoupling[J]. New Journal of Physics, 21, 083040(2019).

[20] Keller J, Burgermeister T, Kalincev D et al. Controlling systematic frequency uncertainties at the 10 -19 level in linear Coulomb crystals[J]. Physical Review A, 99, 013405(2019).

[21] Courtillot I, Quessada A, Kovacich R P et al. Clock transition for a future optical frequency standard with trapped atoms[J]. Physical Review A, 68, 030501(2003).

[22] Ushijima I, Takamoto M, Katori H. Operational magic intensity for Sr optical lattice clocks[J]. Physical Review Letters, 121, 263202(2018).

[23] Akatsuka T, Takamoto M, Katori H. Three-dimensional optical lattice clock with bosonic 88Sr atoms[J]. Physical Review A, 81, 023402(2010).

[24] Campbell S L, Hutson R B, Marti G E et al. A Fermi-degenerate three-dimensional optical lattice clock[J]. Science, 358, 90-94(2017).

[25] Middelmann T, Lisdat C, Falke S et al. Tackling the blackbody shift in a strontium optical lattice clock[J]. IEEE Transactions on Instrumentation and Measurement, 60, 2550-2557(2011).

[26] Ushijima I, Takamoto M, Das M et al. Cryogenic optical lattice clocks[J]. Nature Photonics, 9, 185-189(2015).

[27] Oelker E, Hutson R B, Kennedy C J et al. Demonstration of 4.8×10 -17 stability at 1 s for two independent optical clocks[J]. Nature Photonics, 13, 714-719(2019).

[28] Allan D W. Statistics of atomic frequency standards[J]. Proceedings of the IEEE, 54, 221-230(1966).

[29] Dick G J. Local oscillator induced instabilities in trapped ion frequency standards. [C]∥Proceedings of the Nineteenth Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting, December 1-3, 1987, Redondo Beach, CA. [S.l.: s.n.](1987).

[30] Al-Masoudi A, Dörscher S, Häfner S et al. Noise and instability of an optical lattice clock[J]. Physical Review A, 92, 063814(2015).

[31] Keller J, Ignatovich S, Webster S A et al. Simple vibration-insensitive cavity for laser stabilization at the 10 -16 level[J]. Applied Physics B, 116, 203-210(2014).

[32] Häfner S, Falke S, Grebing C et al. 8×10 -17 fractional laser frequency instability with a long room-temperature cavity[J]. Optics Letters, 40, 2112-2115(2015).

[33] Matei D G, Legero T, Grebing C et al. A second generation of low thermal noise cryogenic silicon resonators[J]. Journal of Physics: Conference Series, 723, 012031(2016).

[34] Zhang W, Robinson J M, Sonderhouse L et al. Ultrastable silicon cavity in a continuously operating closed-cycle cryostat at 4 K[J]. Physical Review Letters, 119, 243601(2017).

[35] Lodewyck J, Westergaard P G, Lemonde P. Nondestructive measurement of the transition probability in a Sr optical lattice clock[J]. Physical Review A, 79, 061401(2009).

[36] Vallet G, Bookjans E, Eismann U et al. A noise-immune cavity-assisted non-destructive detection for an optical lattice clock in the quantum regime[J]. New Journal of Physics, 19, 083002(2017).

[37] Shiga N, Takeuchi M. Locking the local oscillator phase to the atomic phase via weak measurement[J]. New Journal of Physics, 14, 023034(2012).

[38] Kohlhaas R, Bertoldi A, Cantin E et al. Phase locking a clock oscillator to a coherent atomic ensemble[J]. Physical Review X, 5, 021011(2015).

[39] Schioppo M, Brown R C. McGrew W F, et al. Ultrastable optical clock with two cold-atom ensembles[J]. Nature Photonics, 11, 48-52(2017).

[40] Itano W M, Bergquist J C, Bollinger J J et al. Quantum projection noise: population fluctuations in two-level systems[J]. Physical Review A, 47, 3554-3570(1993).

[41] Liu H, Zhang X, Jiang K L et al. Realization of closed-loop operation of optical lattice clock based on 171Yb[J]. Chinese Physics Letters, 34, 020601(2017).

[42] Lu X T, Zhou C H, Li T et al. Synchronous frequency comparison beyond the Dick limit based on dual-excitation spectrum in an optical lattice clock[J]. Applied Physics Letters, 117, 231101(2020).

[43] Lu X T, Yin M J, Li T et al. Demonstration of the frequency-drift-induced self-comparison measurement error in optical lattice clocks[J]. Japanese Journal of Applied Physics, 59, 070903(2020).

[44] Li Y, Lin Y G, Wang Q et al. An improved strontium lattice clock with 10 -16 level laser frequency stabilization[J]. Chinese Optics Letters, 16, 051402(2018).

[45] Beloy K, Bodine M I, Bothwell T et al. Frequency ratio measurements at 18-digit accuracy using an optical clock network[J]. Nature, 591, 564-569(2021).

[46] le Targat R, Lorini L, le Coq Y et al. Experimental realization of an optical second with strontium lattice clocks[J]. Nature Communications, 4, 2109(2013).

[47] Origlia S, Pramod M S, Schiller S et al. Towards an optical clock for space: compact, high-performance optical lattice clock based on bosonic atoms[J]. Physical Review A, 98, 053443(2018).

[48] Ohmae N, Bregolin F, Nemitz N et al. Direct measurement of the frequency ratio for Hg and Yb optical lattice clocks and closure of the Hg/Yb/Sr loop[J]. Optics Express, 28, 15112-15121(2020).

[49] Lin Y G, Wang Q, Meng F et al. A 87Sr optical lattice clock with 2.9×10 -17 uncertainty and its absolute frequency measurement[J]. Metrologia, 58, 035010(2021).

[50] Ovsiannikov V D, Marmo S I, Palchikov V G et al. Higher-order effects on the precision of clocks of neutral atoms in optical lattices[J]. Physical Review A, 93, 043420(2016).

[51] Poli N, Barber Z W, Lemke N D et al. Frequency evaluation of the doubly forbidden 1S0→ 3P0 transition in bosonic 174Yb[J]. Physical Review A, 77, 050501(2008).

[52] Lodewyck J, Zawada M, Lorini L et al. Observation and cancellation of a perturbing dc stark shift in strontium optical lattice clocks[J]. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 59, 411-415(2012).

[53] Beloy K, Zhang X. McGrew W F, et al. Faraday-shielded dc stark-shift-free optical lattice clock[J]. Physical Review Letters, 120, 183201(2018).

[54] Ludlow A D, Zelevinsky T, Campbell G K et al. Sr lattice clock at 1×10 -16 fractional uncertainty by remote optical evaluation with a Ca clock[J]. Science, 319, 1805-1808(2008).

[55] Westergaard P G, Lodewyck J, Lorini L et al. Lattice-induced frequency shifts in Sr optical lattice clocks at the 10 -17 level[J]. Physical Review Letters, 106, 210801(2011).

[56] Falke S, Schnatz H. Winfred J S R V, et al. The 87Sr optical frequency standard at PTB[J]. Metrologia, 48, 399-407(2011).

[57] Bloom B J, Nicholson T L, Williams J R et al. An optical lattice clock with accuracy and stability at the 10 -18 level[J]. Nature, 506, 71-75(2014).

[58] Nicholson T L, Campbell S L, Hutson R B et al. Systematic evaluation of an atomic clock at 2×10 -18 total uncertainty[J]. Nature Communications, 6, 6896(2015).

[59] Lu X T, Yin M J, Li T et al. An evaluation of the Zeeman shift of the 87Sr optical lattice clock at the national time service center[J]. Applied Sciences, 10, 1440(2020).

[60] Falke S, Misera M, Sterr U et al. Delivering pulsed and phase stable light to atoms of an optical clock[J]. Applied Physics B, 107, 301-311(2012).

[61] Peik E, Schneider T, Tamm C. Laser frequency stabilization to a single ion[J]. Journal of Physics B: Atomic, Molecular and Optical Physics, 39, 145-158(2006).

[62] Yuan J B, Cao J, Cui K F et al. Suppression of servo error uncertainty to 10 -18 level using double integrator algorithm in ion optical clock[J]. Chinese Physics B, 30, 070305(2021).

[63] Gao Q, Zhou M, Han C et al. Systematic evaluation of a 171Yb optical clock by synchronous comparison between two lattice systems[J]. Scientific Reports, 8, 8022(2018).

[64] Takamoto M, Hong F L, Higashi R et al. An optical lattice clock[J]. Nature, 435, 321-324(2005).

[65] Takamoto M, Hong F L, Higashi R et al. Improved frequency measurement of a one-dimensional optical lattice clock with a spin-polarized fermionic 87Sr isotope[J]. Journal of the Physical Society of Japan, 75, 104302(2006).

[66] Ludlow A D, Boyd M M, Ye J et al. Optical atomic clocks[J]. Reviews of Modern Physics, 87, 637-701(2015).

[67] Beloy K, Hinkley N, Phillips N B et al. Atomic clock with 1×10 -18 room-temperature blackbody stark uncertainty[J]. Physical Review Letters, 113, 260801(2014).

[68] Campbell G K, Boyd M M, Thomsen J W et al. Probing interactions between ultracold fermions[J]. Science, 324, 360-363(2009).

[69] Lemke N D, von Stecher J, Sherman J A et al. P-wave cold collisions in an optical lattice clock[J]. Physical Review Letters, 107, 103902(2011).

[70] Rey A M, Gorshkov A V, Kraus C V et al. Probing many-body interactions in an optical lattice clock[J]. Annals of Physics, 340, 311-351(2014).

[71] Goban A, Hutson R B, Marti G E et al. Emergence of multi-body interactions in a fermionic lattice clock[J]. Nature, 563, 369-373(2018).

[72] Lee S, Park C Y, Lee W K et al. Cancellation of collisional frequency shifts in optical lattice clocks with Rabi spectroscopy[J]. New Journal of Physics, 18, 033030(2016).

[73] Ludlow A D, Lemke N D, Sherman J A et al. Cold-collision-shift cancellation and inelastic scattering in a Yb optical lattice clock[J]. Physical Review A, 84, 052724(2011).

[74] Swallows M D, Bishof M, Lin Y G et al. Suppression of collisional shifts in a strongly interacting lattice clock[J]. Science, 331, 1043-1046(2011).

[75] Koller S B, Grotti J, Vogt S et al. Transportable optical lattice clock with 7×10 -17 uncertainty[J]. Physical Review Letters, 118, 073601(2017).

[76] Brown R C, Phillips N B, Beloy K et al. Hyperpolarizability and operational magic wavelength in an optical lattice clock[J]. Physical Review Letters, 119, 253001(2017).

[77] Grotti J, Koller S, Vogt S et al. Geodesy and metrology with a transportable optical clock[J]. Nature Physics, 14, 437-441(2018).

[78] Poli N, Schioppo M, Vogt S et al. A transportable strontium optical lattice clock[J]. Applied Physics B, 117, 1107-1116(2014).

[79] Kong D H, Wang Z H, Guo F et al. A transportable optical lattice clock at the national time service center[J]. Chinese Physics B, 29, 070602(2020).

[80] Takamoto M, Ushijima I, Ohmae N et al. Test of general relativity by a pair of transportable optical lattice clocks[J]. Nature Photonics, 14, 411-415(2020).

[81] Ohmae N, Takamoto M, Takahashi Y et al. Transportable strontium optical lattice clocks operated outside laboratory at the level of 10 -18 uncertainty[J]. Advanced Quantum Technologies, 4, 2170015(2021).

[82] Schiller S, Görlitz A, Nevsky A et al. Optical clocks in space[J]. Nuclear Physics B-Proceedings Supplements, 166, 300-302(2007).

[83] Pizzocaro M, Sekido M, Takefuji K et al. Intercontinental comparison of optical atomic clocks through very long baseline interferometry[J]. Nature Physics, 17, 223-227(2021).

[84] Koyama Y. The use of very long baseline interferometry for time and frequency metrology[J]. MAPAN-Journal of Metrology Society of India, 27, 23-30(2012).

[85] Cromartie H T, Fonseca E, Ransom S M et al. Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar[J]. Nature Astronomy, 4, 72-76(2020).

[86] Loh W, Stuart J, Reens D et al. Operation of an optical atomic clock with a Brillouin laser subsystem[J]. Nature, 588, 244-249(2020).

[87] Bongs K, Singh Y, Smith L et al. Development of a strontium optical lattice clock for the SOC mission on the ISS[J]. Comptes Rendus Physique, 16, 553-564(2015).

[89] Wu J, Sun L L, You L et al. Prospect for Chinese space science in 2016-2030[J]. Bulletin of Chinese Academy of Sciences, 30, 707-720(2015).

[90] Dörscher S, Schwarz R, Al-Masoudi A et al. Lattice-induced photon scattering in an optical lattice clock[J]. Physical Review A, 97, 063419(2018).

[91] Norcia M A, Young A W, Eckner W J et al. Seconds-scale coherence on an optical clock transition in a tweezer array[J]. Science, 366, 93-97(2019).

[92] Young A W, Eckner W J, Milner W R et al. Half-minute-scale atomic coherence and high relative stability in a tweezer clock[J]. Nature, 588, 408-413(2020).

[93] Tyumenev R, Favier M, Bilicki S et al. Comparing a mercury optical lattice clock with microwave and optical frequency standards[J]. New Journal of Physics, 18, 113002(2016).

[94] Golovizin A, Fedorova E, Tregubov D et al. Inner-shell clock transition in atomic thulium with a small blackbody radiation shift[J]. Nature Communications, 10, 1724(2019).

[95] Kock O, He W. wierad D, et al. Laser controlled atom source for optical clocks[J]. Scientific Reports, 6, 37321(2016).

[96] Bowden W, Hobson R, Hill I R et al. A pyramid MOT with integrated optical cavities as a cold atom platform for an optical lattice clock[J]. Scientific Reports, 9, 11704(2019).

[97] Lemonde P, Wolf P. Optical lattice clock with atoms confined in a shallow trap[J]. Physical Review A, 72, 033409(2005).

[98] Kolkowitz S, Bromley S L, Bothwell T et al. Spin-orbit-coupled fermions in an optical lattice clock[J]. Nature, 542, 66-70(2017).

[99] Hutson R B, Goban A, Marti G E et al. Engineering quantum states of matter for atomic clocks in shallow optical lattices[J]. Physical Review Letters, 123, 123401(2019).

[100] Yin Mo J, Wang T, Lu X T et al. -10-14)[2021-11-08]. https:∥arxiv., org/abs/2110, 07169(2021).