8  ×  10^−17 fractional laser frequency instability with a long room-temperature cavity

Häfner, Sebastian; Falke, Stephan; Grebing, Christian; Vogt, Stefan; Legero, Thomas; Merimaa, Mikko; Lisdat, Christian; Sterr, U.

doi:10.1364/ol.40.002112

Cited by 228 publications

(170 citation statements)

References 23 publications

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“…This is roughly an order of magnitude reduction in the shift and a factor of 50 reduction in the uncertainty due to secular motion time-dilation in comparison with −(16.3 ± 5.0) × 10 −18 reported in the previous 27 Al + optical clock [8]. Extending the clock interrogation time to 1 s [28][29][30][31], the fractional time-dilation shift due to secular motion is estimated to be −(5.7 ± 0.3) × 10 −18 .…”

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confidence: 56%

Sympathetic Ground State Cooling and Time-Dilation Shifts in an Al27+ Optical Clock

et al. 2017

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We report on Raman sideband cooling of 25 Mg + to sympathetically cool the secular modes of motion in a 25 Mg + -27 Al + two-ion pair to near the three-dimensional (3D) ground state. The evolution of the Fock-state distribution during the cooling process is studied using a rate-equation simulation, and various heating sources that limit the efficiency of 3D sideband cooling in our system are discussed. We characterize the residual energy and heating rates of all of the secular modes of motion and estimate a secular motion time-dilation shift of −(1.9 ± 0.1) × 10 −18 for an 27 Al + clock at a typical clock probe duration of 150 ms. This is a 50-fold reduction in the secular motion time-dilation shift uncertainty in comparison with previous 27 Al + clocks. Trapped and laser-cooled ions are useful for many applications in quantum information processing and quantum metrology because of their isolation from the ambient environment and mutual Coulomb interaction [1][2][3][4][5][6]. The Coulomb interaction establishes normal modes of motion, called secular modes, which enable information exchange and entanglement between ions. For many operations in quantum information processing and metrology, these secular modes should ideally be prepared in their ground state. For example, in state-of-the-art trapped-ion optical clocks [7], uncertainty in the Doppler shift due to the residual excitation of these modes is a dominant contribution to the total clock uncertainty [8][9][10].All trapped-ion optical clocks to date have been operated with the ions' motion near the Doppler cooling limit [7][8][9][10]. For clocks based on quantum-logic spectroscopy of the 1 S 0 ↔ 3 P 0 transition in 27 Al + [11], the smallest uncertainty has been achieved by performing continuous sympathetic Doppler cooling on the logic ion ( 25 Mg + ) during the clock interrogation [8]. Due to the difficulty of performing accurate temperature measurements of trapped ions near the Doppler cooling limit, the uncertainty of the secular motion temperature was limited to 30 % [8].To reduce the secular motion time-dilation shift and its uncertainty, sub-Doppler cooling techniques can be employed [12][13][14][15][16][17]. These schemes have not previously been implemented in ion-based clock experiments due to high ambient motional heating rates, the need for extra cooling laser beams, and the difficulty of characterizing the resulting motional state distribution, which can be nonthermal [8,10,18]. For example, in sideband cooling, a non-thermal distribution can result from zero-crossings in the cooling transition Rabi rate as a function of the Fock state [19,20] and from cooling durations insufficient to reach equilibrium. Although sideband cooling can reach extremely low energies, a small non-thermal component of the distribution may contribute more than 90 % of the total energy [21], rendering the temperature measurement technique using motional sideband ratios unsuitable for determining the energy [12,13].Here we demonstrate sympathetic cooling of a 25 Mg + -27 ...

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confidence: 56%

Sympathetic Ground State Cooling and Time-Dilation Shifts in an Al27+ Optical Clock

et al. 2017

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“…This is roughly an order of magnitude reduction in the shift and a factor of 50 reduction in the uncertainty due to secular motion time dilation in comparison with −ð16.3 AE 5.0Þ × 10 −18 , reported in the previous 27 Al þ optical clock [8]. Extending the clock interrogation time to 1 s [33][34][35][36], the fractional time-dilation shift due to secular motion is estimated to be −ð5.7 AE 0.3Þ × 10 −18 .…”

Section: Prl 118 053002 (2017) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 61%

Trapped Ions Stopped Cold

Huntemann

2017

Physics

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We report on Raman sideband cooling of 25 Mg þ to sympathetically cool the secular modes of motion in a 25 Mg þ -27 Al þ two-ion pair to near the three-dimensional (3D) ground state. The evolution of the Fock-state distribution during the cooling process is studied using a rate-equation simulation, and various heating sources that limit the efficiency of 3D sideband cooling in our system are discussed. We characterize the residual energy and heating rates of all of the secular modes of motion and estimate a secular motion time-dilation shift of −ð1.9 AE 0.1Þ × 10 −18 for an 27 Al þ clock at a typical clock probe duration of 150 ms. This is a 50-fold reduction in the secular motion time-dilation shift uncertainty in comparison with previous 27 Al þ clocks. DOI: 10.1103/PhysRevLett.118.053002 Trapped and laser-cooled ions are useful for many applications in quantum information processing and quantum metrology because of their isolation from the ambient environment and the mutual Coulomb interaction [1][2][3][4][5][6]. The Coulomb interaction establishes normal modes of motion, called secular modes, which enable information exchange and entanglement between ions. For many operations in quantum information processing and metrology, these secular modes should, ideally, be prepared in their ground state. For example, in state-of-the-art trappedion optical clocks [7], uncertainty in the Doppler shift due to the residual excitation of these modes is a dominant contribution to the total clock uncertainty [8][9][10].All trapped-ion optical clocks to date have been operated with the ions' motion near the Doppler cooling limit [7][8][9][10]. For clocks based on quantum-logic spectroscopy of the 1 S 0 ↔ 3 P 0 transition in 27 Al þ [11], the smallest uncertainty has been achieved by performing continuous sympathetic Doppler cooling on the logic ion ( 25 Mg þ ) during the clock interrogation [8]. Because of the difficulty of performing accurate temperature measurements of trapped ions near the Doppler cooling limit, the uncertainty of the secular motion temperature was limited to 30% [8].To reduce the secular motion time-dilation shift and its uncertainty, sub-Doppler cooling techniques can be employed [12][13][14][15][16][17]. These schemes have not previously been implemented in ion-based clock experiments due to high ambient motional heating rates, the need for extra cooling laser beams, and the difficulty of characterizing the resulting motional state distribution, which can be nonthermal [8,10,18]. For example, in sideband cooling, a nonthermal distribution can result from zero crossings in the cooling transition Rabi rate as a function of the Fock state [19,20] and from cooling durations insufficient to reach equilibrium. Although sideband cooling can reach extremely low energies, a small nonthermal component of the distribution may contribute more than 90% of the total energy [21], rendering the temperature measurement technique using motional sideband ratios unsuitable for determining the energy [12,13].Here, we dem...

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“…20) As the sensitivity ½ðg n c =g 0 Þ 2 þ ðg n s =g 0 Þ 2 1=2 rapidly decreases for f ≫ 1=T i , frequency noise with low Fourier components of a few Hz solely affects the clock instability σ Dick . Note that the frequency noise of the clock laser with the state-of-theart instability of σ y ∼ 1 × 10 −16 at τ = 1 s [25][26][27] [green line in Fig. 4(a)] is an order of magnitude larger than the frequency transfer noise of the comb for f < 100 Hz, where the Dick effect plays a decisive role.…”

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confidence: 99%

All-polarization-maintaining, single-port Er:fiber comb for high-stability comparison of optical lattice clocks

Ohmae

Kuse²,

Fermann³

et al. 2017

Appl. Phys. Express

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All-polarization-maintaining, single-port Er:fiber combs offer long-term robust operation as well as high stability. We have built two such combs and evaluated the transfer noise for linking optical clocks. A uniformly broadened spectrum over 135-285 THz with a high signal-to-noise ratio enables the optical frequency measurement of the subharmonics of strontium, ytterbium, and mercury optical lattice clocks with the fractional frequencynoise power spectral density of (1-2) ' 10 %17 Hz %1/2 at 1 Hz. By applying a synchronous clock comparison, the comb enables clock ratio measurements with 10 %17 instability at 1 s, which is one order of magnitude smaller than the best instability of the frequency ratio of optical lattice clocks. © 2017 The Japan Society of Applied PhysicsO ptical frequency combs have become indispensable tools for precision measurements including atomic= molecular spectroscopy, low-phase-noise microwave generation, and ranging. 1) In optical clocks, linking different atomic clocks 2,3) or distant clocks via optical fibers 4) with a fractional uncertainty of 10 −18 is of significant concern with a future redefinition of the second in the International System of Units (SI). 5) Such endeavors, in turn, offer intriguing opportunities for testing the constancy of the fundamental constants 6) and for relativistic geodesy. 4,7) These applications necessitate ultralow-noise optical frequency combs that allow long-term and robust operation. Titanium-sapphire-based frequency combs have demonstrated outstanding stability. 8,9) However, their bulky optical setups require regular maintenance, thus hampering long-term and robust operation, which limits their potential applications. In contrast, erbium (Er) fiber combs enable all-fiber architecture for robust operation. Although a typical Er:fiber comb uses nonlinear polarization rotation (NPR) to acquire mode-locking with excellent noise performance, 9-13) the operational condition for such NPR-based Er:fiber oscillators can be sensitive to environmental conditions. For practical applications, such as the longterm operation of clocks to generate the optical second 14) and field and space applications, the all-polarization-maintaining (PM) architecture is preferred. 15,16) However, such architecture has shown relatively large phase noise. Low intrinsic phase noise with PM architecture is demonstrated by applying a nonlinear amplifying loop mirror (NALM). 17,18) In linking multiple optical frequencies, Er:fiber combs with a multibranch configuration, where each port consists of an Er-doped fiber amplifier (EDFA) and a highly nonlinear fiber (HNLF), have been employed, 3,19) as it allows sufficient output power per comb tooth optimized for the single frequency. In such a multibranch comb, the phase noise in different branches introduces the instability of ∼10 −16 at 1 s. 10,11) A record high instability of 4 × 10 −16 (τ=s) −1=2 has been demonstrated for synchronous clock comparison between strontium (Sr)-and ytterbium (Yb)-based optical lattice clocks, 3) in whic...

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8 × 10^−17 fractional laser frequency instability with a long room-temperature cavity

Cited by 228 publications

References 23 publications

Sympathetic Ground State Cooling and Time-Dilation Shifts in an Al27+ Optical Clock

Sympathetic Ground State Cooling and Time-Dilation Shifts in an Al27+ Optical Clock

Trapped Ions Stopped Cold

All-polarization-maintaining, single-port Er:fiber comb for high-stability comparison of optical lattice clocks

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