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Uncertainty evaluation of an 171Yb optical lattice clock at NMIJ
摘要： We report an uncertainty evaluation of an 171Yb optical lattice clock with a total fractional uncertainty of 3.6 × 10^{-16}, which is mainly limited by the lattice-induced light shift and the blackbody radiation shift. Our evaluation of the lattice-induced light shift, the density shift, and the second-order Zeeman shift is based on an interleaved measurement where we measure the frequency shift using the alternating stabilization of a clock laser to the 6s2 1S0–6s6p 3P0 clock transition with two different experimental parameters. In the present evaluation, the uncertainties of two sensitivity coefficients for the lattice-induced hyperpolarizability shift d incorporated in a widely used light shift model by RIKEN and the second-order Zeeman shift aZ are improved compared with the uncertainties of previous coefficients. The hyperpolarizability coefficient d is determined by investigating the trap potential depth and the light shifts at the lattice frequencies near the two-photon transitions 6s6p3P0–6s8p3P0, 6s8p3P2, and 6s5f3F2. The obtained values are d = ?1.1(4) μHz and aZ = ?6.6(3) Hz/mT2. These improved coefficients should reduce the total systematic uncertainties of Yb lattice clocks at other institutes.
关键词： precise measurement,optical lattice clock,optical frequency comb,Frequency standards,SI second
更新于2025-09-23 15:23:52
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Quantum phase transition modulation in an atomtronic Mott switch
摘要： Mott insulators provide stable quantum states and long coherence times due to small number fluctuations, making them good candidates for quantum memory and atomic circuits. We propose a proof-of-principle for a 1D Mott switch using an ultracold Bose gas and optical lattice. With time-evolving block decimation simulations—efficient matrix product state methods—we design a means for transient parameter characterization via a local excitation for ease of engineering into more complex atomtronics. We perform the switch operation by tuning the intensity of the optical lattice, and thus the interaction strength through a conductance transition due to the confined modifications of the 'wedding cake' Mott structure. We demonstrate the time-dependence of Fock state transmission and fidelity of the excitation as a means of tuning up the device in a double well and as a measure of noise performance. Two-point correlations via the g(2) measure provide additional information regarding superfluid fragments on the Mott insulating background due to the confinement of the potential.
关键词： quantum gas,atomtronic switch,optical lattice,atomtronics,quantum phase transition,matrix product states,Mott insulator
更新于2025-09-23 15:23:52
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Atomic clock performance enabling geodesy below the centimetre level
摘要： The passage of time is tracked by counting oscillations of a frequency reference, such as Earth’s revolutions or swings of a pendulum. By referencing atomic transitions, frequency (and thus time) can be measured more precisely than any other physical quantity, with the current generation of optical atomic clocks reporting fractional performance below the 10?17 level1–5. However, the theory of relativity prescribes that the passage of time is not absolute, but is affected by an observer’s reference frame. Consequently, clock measurements exhibit sensitivity to relative velocity, acceleration and gravity potential. Here we demonstrate local optical clock measurements that surpass the current ability to account for the gravitational distortion of space-time across the surface of Earth. In two independent ytterbium optical lattice clocks, we demonstrate unprecedented values of three fundamental benchmarks of clock performance. In units of the clock frequency, we report systematic uncertainty of 1.4 × 10?18, measurement instability of 3.2 × 10?19 and reproducibility characterized by ten blinded frequency comparisons, yielding a frequency difference of [?7 ± (5)stat ± (8)sys] × 10?19, where ‘stat’ and ‘sys’ indicate statistical and systematic uncertainty, respectively. Although sensitivity to differences in gravity potential could degrade the performance of the clocks as terrestrial standards of time, this same sensitivity can be used as a very sensitive probe of geopotential5–9. Near the surface of Earth, clock comparisons at the 1 × 10?18 level provide a resolution of one centimetre along the direction of gravity, so the performance of these clocks should enable geodesy beyond the state-of-the-art level. These optical clocks could further be used to explore geophysical phenomena10, detect gravitational waves11, test general relativity12 and search for dark matter13–17.
关键词： geodesy,ytterbium,atomic clock,dark matter,geopotential,gravitational waves,relativity,optical lattice clocks
更新于2025-09-23 15:21:01
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[IEEE 2019 Joint Conference of the IEEE International Frequency Control Symposium anEuropean Frequency and Time Forum (EFTF/IFC) - Orlando, FL, USA (2019.4.14-2019.4.18)] 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC) - Ultrastable Laser System Using Room-Temperature Optical Cavity with 4.8??10 <sup>a??17</sup> Thermal Noise Limit
摘要： A new clock laser system using an optical cavity with 4.8×10-17 thermal noise limit has been developed for rapid evaluation of ytterbium lattice clocks. This was realized by using a 30-cm-long ULE cavity, fused-silica mirror substrates, and crystalline mirror coatings. The frequency stability of the beating signal between the new clock laser and the old clock laser was limited by the latter. The linewidth and the frequency stability of the new clock laser will be measured by comparing the frequency between two similar systems.
关键词： linewidth,ytterbium,optical lattice clock,frequency stability,optical cavity,clock laser,crystalline coating
更新于2025-09-19 17:13:59
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Accurate laser frequency locking to optical frequency combs under low-signal-to-noise-ratio conditions
摘要： We demonstrate a method for accurately locking the frequency of a continuous-wave laser to an optical frequency comb under conditions where the signal-to-noise ratio is low, too low to accommodate other methods. Our method is typically orders of magnitude more accurate than conventional wavemeters and can considerably extend the usable wavelength range of a given optical frequency comb. We illustrate our method by applying it to the frequency control of a dipole lattice trap for an optical lattice clock, a representative case where our method provides significantly better accuracy than other methods.
关键词： optical lattice clock,optical frequency combs,laser frequency locking,low-signal-to-noise-ratio
更新于2025-09-19 17:13:59
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The Effect of Internal Dynamics on the Motion of Cold Atoms in 2D Optical Lattices with Interfering Laser Beams
摘要： We show theoretically and numerically that cold two-level atoms demonstrate unexpectedly complicated motion in an absolutely rigid two-dimensional optical lattice with interfering laser beams. The point-like atoms can move there in a chaotic way resembling motion of particles in a random potential. Chaos arises if the laser frequency is close to the atomic transition frequency where one should take into account the excitation of internal atomic states by the laser field. After loading cold atoms to the lattice, their induced electric dipole moments interact with a spatially inhomogeneous electric field of the two-dimensional standing laser wave. We find the range of the atom–field detuning where the synchronized (with the laser field) component of the atomic dipole moment changes in a random-like manner just after crossing the nodal lines of the standing wave where the electric field is zero. It, in turn, causes irregular changes in the momentum of atoms, leading eventually to chaotic walking of cold atoms in a deterministic potential. We show that adjusting the single control parameter, the atom–field detuning, it is possible to switch between regular and chaotic regimes of motion.
关键词： 2D optical lattice,interfering laser beams,chaotic walking,cold atoms
更新于2025-09-19 17:13:59
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Noise Sensitivities for an Atom Shuttled by a Moving Optical Lattice via Shortcuts to Adiabaticity
摘要： We ?nd the noise sensitivities (i.e., the quadratic terms of the energy with respect to the perturbation of the noise) of a particle shuttled by an optical lattice that moves according to a shortcut-to-adiabaticity transport protocol. Noises affecting different optical lattice parameters, trap depth, position, and lattice periodicity, are considered. We ?nd generic expressions of the sensitivities for arbitrary noise spectra but focus on the white-noise limit as a basic reference, and on Ornstein–Uhlenbeck noise to account for the effect of non-zero correlation times.
关键词： shortcuts to adiabaticity,invariant-based inverse engineering,transport,noise sensitivities,optical lattice
更新于2025-09-16 10:30:52
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Optical Frequency Measurements at 1×10?18 Uncertainty with Ytterbium Optical Lattice Clocks
摘要： We describe ytterbium optical lattice clocks under development at NIST. This includes the characterization of optical frequency stability and uncertainty, as well as measurements between two independent clocks, at the 10-18 level. We also report on optical frequency ratio measurements with other optical clocks at NIST.
关键词： precision frequency,optical lattice,optical standard,ytterbium,frequency measurement,uncertainty,optical ratio,optical clock
更新于2025-09-10 09:29:36
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Selective population of a large-angular-momentum state in an optical lattice
摘要： We propose a method to selectively populate a large-angular-momentum state of ultracold atoms (each with an orbital angular momentum l ≈ 2 ˉh) in the Mott regime of a two-dimensional optical lattice. This is done by periodically modulating the lattice amplitude and implementing an additional rotated rectangular lattice of shorter wavelength. The speci?c pulse sequences are designed using a four-level model for each well and are implemented sequentially. The results are con?rmed with numerical simulations of the full Schr?dinger equation. These methods are another step in constructing a modular toolbox of operations for creating higher orbital states in optical lattices.
关键词： optical lattice,angular momentum,Schr?dinger equation,ultracold atoms,Mott regime
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Study of Accuracy and Stability of Sr Lattice Clocks at LNE-SYRTE
摘要： In this paper, we describe the operation of two optical lattice clocks operated at LNE-SYRTE. They feature an accuracy down to 2.1 × 10?17, and each clock has a fractional frequency stability of 7 × 10?16/√τ. We propose the updated accuracy budget of these clocks, with specific evaluations of the lattice-induced effect, as well as the characterization of a spurious systematic effect due to electric cross-talk between the clocks cycle and the clock laser that was recently observed. Reliably operating these two clocks led to the first contribution of an optical clock to TAI. Finally, we report on a non-destructive detection scheme aiming at improving the clock stability.
关键词： non-destructive detection,Optical lattice clocks,TAI
更新于2025-09-10 09:29:36