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arXiv:2506.09031 · Physical Review Research

Isotope-agnostic motional ground-state cooling of neutral Yb atoms

Ronen M. Kroeze, René A. Villela, Er Zu, Tim O. Höhn, Monika Aidelsburger

Published Nov 10, 2025• 1 citation
arXivHTMLPDF

Abstract

Efficient high-fidelity ground-state cooling of motional degrees of freedom is crucial for applications in quantum simulation, computing, and metrology. Here, we demonstrate direct ground-state cooling of fermionic Yb 171 and bosonic Yb 174 atoms in two- and three-dimensional magic-wavelength optical lattices on the ultranarrow clock transition. Its high spectral resolution offers the potential for reaching extremely low temperatures. To ensure efficient cooling, we develop a chirped sideband cooling scheme, where we sweep the clock-laser frequency to mitigate the effects of spatial trap inhomogeneities. We further generalize the theoretical description of sideband spectra to higher-dimensional lattices for precise thermometry. We achieve 2D ground-state fractions of 97 % for Yb 171 with an average motional occupation of n ¯ ≃ 0.015 and provide a direct comparison with Yb 174 , reaching similar cooling performance. Applying the same scheme in 3D results in n ¯ ≃ 0.15 limited by layer-to-layer inhomogeneities in the vertical direction. These results demonstrate efficient motional ground-state cooling in optical lattices, especially for bosonic alkaline-earth(-like) atoms, where other methods are not applicable, opening the door to novel protocols for quantum science applications with neutral atoms.

DOI
10.1103/dts5-kxsx

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Efficient high-fidelity ground-state cooling of motional degrees of freedom is crucial for applications in quantum simulation, computing, and metrology. Here, we demonstrate direct ground-state cooling of fermionic Yb 171 and bosonic Yb 174 atoms in two- and three-dimensional magic-wavelength optical lattices on the ultranarrow clock transition. Its high spectral resolution offers the potential for reaching extremely low temperatures. To ensure efficient cooling, we develop a chirped sideband cooling scheme, where we sweep the clock-laser frequency to mitigate the effects of spatial trap inhomogeneities. We further generalize the theoretical description of sideband spectra to higher-dimensional lattices for precise thermometry. We achieve 2D ground-state fractions of 97 % for Yb 171 with an average motional occupation of n ¯ ≃ 0.015 and provide a direct comparison with Yb 174 , reaching similar cooling performance. Applying the same scheme in 3D results in n ¯ ≃ 0.15 limited by layer-to-layer inhomogeneities in the vertical direction. These results demonstrate efficient motional ground-state cooling in optical lattices, especially for bosonic alkaline-earth(-like) atoms, where other methods are not applicable, opening the door to novel protocols for quantum science applications with neutral atoms.
Laser cooling of single atoms in optical tweezers is a prerequisite for neutral atom quantum computing and simulation. Resolved sideband cooling comprises a well-established method for efficient motional ground-state preparation, but typically requires careful cancellation of light shifts in so-called magic traps. Here, we study a novel laser cooling scheme which overcomes such constraints, and applies when the ground state of a narrow cooling transition is trapped stronger than the excited state. We demonstrate our scheme, which exploits sequential addressing of red sideband transitions via frequency chirping of the cooling light, at the example of 88Sr^{88}\mathrm{Sr}88Sr atoms and report ground-state populations compatible with recent experiments in magic tweezers. The scheme also induces light-assisted collisions, which are key to the assembly of large atom arrays. Our work enriches the toolbox for tweezer-based quantum technology, also enabling applications for tweezer-trapped molecules and ions that are incompatible with resolved sideband cooling conditions.
Precise state-dependent control of optical potentials is of great importance for various applications utilizing cold neutral atoms. In particular, tune-out wavelengths for the clock state pair in alkaline-earth(-like) atoms provide maximally state-selective trap conditions that hold promise for the realization of novel approaches in quantum computation and simulation. While several ground-state tune-out wavelengths have been determined, similar experimental studies for metastable excited states are challenged by inelastic collisions and Raman losses, so far prohibiting precise measurements of excited-state tune-out conditions. In this work we report on the measurement of a tune-out wavelength for the metastable 3 P 0 clock state in 174 Yb at 519.920 ( 9 ) THz. In order to circumvent collisional losses, we isolate individual 3 P 0 atoms in a two-dimensional clock-magic-wavelength lattice at 759 nm. To minimize the limitation imposed by Raman scattering, we further implement resolved sideband cooling on the clock transition, which allows us to reduce the lattice depth and surpass lifetimes of 5 s. The precision of the tune-out measurement is further enhanced by fluorescence imaging in a triple-magic configuration, where we implement molasses cooling on the 3 P 1 intercombination line and identify a magic angle of 38.5 ( 9 ) ∘ in the clock-magic lattice.
Sideband cooling is a key technique for improving the performance of optical atomic clocks by preparing cold atoms and single ions into the ground vibrational state. In this work, we demonstrate detailed experimental research on pulsed Raman sideband cooling in a 171Yb optical lattice clock. A sequence comprised of interleaved 578 nm cooling pulses resonant on the 1st-order red sideband and 1388 nm repumping pulses is carried out to transfer atoms into the motional ground state. We successfully decrease the axial temperature of atoms in the lattice from 6.5 μK to less than 0.8 μK in the trap depth of 24 μK, corresponding to an average axial motional quantum number 〈 nz 〉 < 0.03. Rabi oscillation spectroscopy is measured to evaluate the effect of sideband cooling on inhomogeneous excitation. The maximum excitation fraction is increased from 0.8 to 0.86, indicating an enhancement in the quantum coherence of the ensemble. Our work will contribute to improving the instability and uncertainty of Yb lattice clocks.
Optical lattice clocks have demonstrated unprecedented performance below the 10^-18 fractional level, advancing towards new standards of timekeeping and sensitive probes in fundamental physics. To further advance optical lattice clocks performance, it is crucial to attain lower temperatures which facilitates the use of shallow lattices with reduced light shifts, while retaining large atom numbers to reduce the quantum projection noise. Here, we present Sisyphus cooling using the long-lived 3P0 clock state in alkaline-earth-like ytterbium. Upon excitation on the ultranarrow clock transition, Sisyphus cooling is observed within a spatially periodic potential induced by a 1388-nm optical standing wave that is nearly resonant with the 3P0 → 3D1 transition. Our cooling demonstrates versatility, working both in free space and in a magic-wavelength lattice. It offers the flexibility of being employed in either pulsed or continuous modes, making it suitable to a range of quantum metrology applications.
Abstract Effcient population transfer and motional state control are important for optical lattice clocks and precision experiments with lattice-trapped neutral atoms. Here we experimentally investigate adiabatic rapid passage (ARP) on the clock transition of a one-dimensional 87 Sr optical lattice clock and develop a mode-resolved model for ARP on motional sidebands. On the carrier transition, ARP enables robust internal-state transfer with a maximum excitation fraction of 0.98(2). On the blue motional sideband, ARP increases the maximum excitation fraction from 0.47(2) to 0.55(3), and the measured dynamics are consistently reproduced by the mode-resolved model. The model further predicts that the sideband transfer effciency can exceed 0.88 when the carrier Rabi frequency is increased to 15 kHz. Applying ARP to the red-sideband cooling reduces the axial mean vibrational occupation to approximately 0.038, corresponding to a motional ground-state population of 0.96. These results provide a quantitative basis for designing ARP excitation on motional sidebands and for optimizing sideband cooling in lattice-trapped atoms, with direct relevance to coherent state preparation in optical lattice clocks and related precision-measurement experiments in neutral atoms.
We propose a cooling scheme for realizing single-photon sideband cooling on particles trapped in a statedependent optical potential.We develop a master rate equation from an ab initio model and find that in experimentally feasible conditions it is possible to reduce the average occupation number of the vibrational levels in one dimension by more than 90% by applying a frequency sweep on the cooling laser that sequentially cools all the motional states.Notably, this cooling scheme works also when a particle experiences a deeper trap in its internal ground state than in its excited state, a condition for which conventional single-photon sideband cooling does not work.In our analysis, we consider two cases: a two-level particle confined in an optical tweezer, and Li atoms confined in an optical lattice, and we find conditions for efficient cooling in both cases.The results from the model are confirmed by a full quantum Monte Carlo simulation of the system Hamiltonian.Our findings provide an alternative cooling scheme that can be applied in principle to any particle, e.g., atoms, molecules, or ions, confined in a state-dependent optical potential.