We propose quantum simulation experiments of the Kondo impurity problem using cold alkaline-earth(-like) atoms (AEAs) in a combination of optical lattice and optical tweezer potentials. Within an ab initio model for atomic interactions in the optical potentials, we analyze hallmark signatures of the Kondo effect in a variety of observables accessible in cold-atom quantum simulators. We identify additional terms not part of the textbook Kondo problem, mostly ignored in previous works and giving rise to a direct competition between spin and charge correlations, strongly suppressing Kondo physics. We show that the Kondo effect can be restored by locally adjusting the chemical potential on the impurity site, and we identify realistic parameter regimes and preparation protocols suited to current experiments with AEA arrays. Our work paves the way for quantum simulations of the Kondo problem and offers insights into Kondo physics in unconventional regimes.
", "doi": "10.1103/m7l3-y2f8", "issn": "2469-9926", "publisher": "American Physical Society", "publication": "Physical Review A", "publication_date": "2025-10-01", "series_number": "4", "volume": "112", "issue": "4", "pages": "043301" }, { "id": "authors:52d3w-r3f96", "collection": "authors", "collection_id": "52d3w-r3f96", "cite_using_url": "https://authors.library.caltech.edu/records/52d3w-r3f96", "type": "monograph", "title": "Multi-qubit gates and 'Schr\u00f6dinger cat' states in an optical clock", "author": [ { "family_name": "Cao", "given_name": "Alec", "orcid": "0000-0002-6111-1375", "clpid": "Cao-Alec" }, { "family_name": "Eckner", "given_name": "William J.", "orcid": "0000-0003-0833-7137", "clpid": "Eckner-William-J" }, { "family_name": "Lukin Yelin", "given_name": "Theodor", "orcid": "0009-0000-7295-5701", "clpid": "Lukin-Yelin-Theodor" }, { "family_name": "Young", "given_name": "Aaron W.", "orcid": "0000-0002-3490-4046", "clpid": "Young-Aaron-W" }, { "family_name": "Jandura", "given_name": "Sven", "orcid": "0000-0003-0282-7637", "clpid": "Jandura-Sven" }, { "family_name": "Yan", "given_name": "Lingfeng", "clpid": "Yan-Lingfeng" }, { "family_name": "Kim", "given_name": "Kyungtae", "orcid": "0000-0001-5428-6700", "clpid": "Kim-Kyungtae" }, { "family_name": "Pupillo", "given_name": "Guido", "orcid": "0000-0002-1549-0386", "clpid": "Pupillo-Guido" }, { "family_name": "Ye", "given_name": "Jun", "clpid": "Ye-Jun" }, { "family_name": "Darkwah Oppong", "given_name": "Nelson", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Kaufman", "given_name": "Adam M.", "orcid": "0000-0003-4956-5814", "clpid": "Kaufman-Adam-M" } ], "abstract": "Many-particle entanglement is a key resource for achieving the fundamental precision limits of a quantum sensor. Optical atomic clocks, the current state-of-the-art in frequency precision, are a rapidly emerging area of focus for entanglement-enhanced metrology. Augmenting tweezer-based clocks featuring microscopic control and detection with the high-fidelity entangling gates developed for atom-array information processing offers a promising route towards leveraging highly entangled quantum states for improved optical clocks. Here we develop and employ a family of multi-qubit Rydberg gates to generate 'Schrödinger cat' states of the Greenberger-Horne-Zeilinger (GHZ) type with up to 9 optical clock qubits in a programmable atom array. In an atom-laser comparison at sufficiently short dark times, we demonstrate a fractional frequency instability below the standard quantum limit using GHZ states of up to 4 qubits. A key challenge to improving the optimal achievable clock precision with GHZ states is their reduced dynamic range. Towards overcoming this hurdle, we simultaneously prepare a cascade of varying-size GHZ states to perform unambiguous phase estimation over an extended interval. These results demonstrate key building blocks for approaching Heisenberg-limited scaling of optical atomic clock precision.
", "doi": "10.48550/arxiv.2402.16289", "publisher": "arXiv", "publication_date": "2024-02-26" }, { "id": "authors:q2f9g-49521", "collection": "authors", "collection_id": "q2f9g-49521", "cite_using_url": "https://authors.library.caltech.edu/records/q2f9g-49521", "type": "article", "title": "Equation of State and Thermometry of the 2D SU\u2061(\ud835\udc41) Fermi-Hubbard Model", "author": [ { "family_name": "Pasqualetti", "given_name": "G.", "clpid": "Pasqualetti-G" }, { "family_name": "Bettermann", "given_name": "O.", "clpid": "Bettermann-O" }, { "family_name": "Darkwah Oppong", "given_name": "N.", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Ibarra-Garc\u00eda-Padilla", "given_name": "E.", "orcid": "0000-0001-9165-0444", "clpid": "Ibarra-Garc\u00eda-Padilla-Eduardo" }, { "family_name": "Dasgupta", "given_name": "S.", "orcid": "0000-0001-6162-6769", "clpid": "Dasgupta-Sohail" }, { "family_name": "Scalettar", "given_name": "R.\u2009T.", "orcid": "0000-0002-0521-3692", "clpid": "Scalettar-Richard-T" }, { "family_name": "Hazzard", "given_name": "K.\u2009R.\u2009A.", "orcid": "0000-0003-2894-7274", "clpid": "Hazzard-Kaden-R-A" }, { "family_name": "Bloch", "given_name": "I.", "orcid": "0000-0002-0679-4759", "clpid": "Bloch-Immanuel" }, { "family_name": "F\u00f6lling", "given_name": "S.", "orcid": "0000-0002-6951-3651", "clpid": "F\u00f6lling-Simon" } ], "abstract": "We characterize the equation of state (EoS) of the SU\u2061(\ud835\udc41 > 2) Fermi-Hubbard Model (FHM) in a two-dimensional single-layer square optical lattice. We probe the density and the site occupation probabilities as functions of interaction strength and temperature for \ud835\udc41 = 3, 4, and 6. Our measurements are used as a benchmark for state-of-the-art numerical methods including determinantal quantum Monte Carlo and numerical linked cluster expansion. By probing the density fluctuations, we compare temperatures determined in a model-independent way by fitting measurements to numerically calculated EoS results, making this a particularly interesting new step in the exploration and characterization of the SU\u2061(\ud835\udc41) FHM.
", "doi": "10.1103/physrevlett.132.083401", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2024-02-23", "series_number": "8", "volume": "132", "issue": "8", "pages": "083401" }, { "id": "authors:6g0g9-mm540", "collection": "authors", "collection_id": "6g0g9-mm540", "cite_using_url": "https://authors.library.caltech.edu/records/6g0g9-mm540", "type": "article", "title": "State-dependent potentials for the \u00b9\ud835\udc46\u2080 and \u00b3\ud835\udc43\u2080 clock states of neutral ytterbium atoms", "author": [ { "family_name": "H\u00f6hn", "given_name": "Tim O.", "clpid": "H\u00f6hn-Tim-O" }, { "family_name": "Staub", "given_name": "Etienne", "clpid": "Staub-Etienne" }, { "family_name": "Brochier", "given_name": "Guillaume", "orcid": "0000-0002-5505-9072", "clpid": "Brochier-Guillaume" }, { "family_name": "Darkwah Oppong", "given_name": "Nelson", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Aidelsburger", "given_name": "Monika", "orcid": "0000-0002-9476-3337", "clpid": "Aidelsburger-Monika" } ], "abstract": "We present measurements of three distinctive state-dependent wavelengths for the ¹\ud835\udc46\u2080−³\ud835\udc43\u2080 clock transition in ¹\u2077\u2074Yb atoms. Specifically, we determine two magic wavelengths at 652.281(21) and 542.50205\u2062(19)\u2062THz, where the differential light shift on the ¹\ud835\udc46\u2080−³\ud835\udc43\u2080 clock transition vanishes, and one tune-out wavelength at 541.8325\u2062(5)\u2062THz, where the polarizability of the ¹\ud835\udc46\u2080 ground state exhibits a zero crossing. The two magic wavelengths are identified by spectroscopically interrogating cold ¹\u2077\u2074Yb atoms on the clock transition in a one-dimensional optical lattice. The ground-state tune-out wavelength is determined via a parametric heating scheme. With a simple empirical model, we then extrapolate the ground- and excited-state polarizability over a broad range of wavelengths in the visible spectrum.
", "doi": "10.1103/physreva.108.053325", "issn": "2469-9926", "publisher": "American Physical Society", "publication": "Physical Review A", "publication_date": "2023-11", "series_number": "5", "volume": "108", "issue": "5", "pages": "053325" }, { "id": "authors:k0e4q-9pt77", "collection": "authors", "collection_id": "k0e4q-9pt77", "cite_using_url": "https://authors.library.caltech.edu/records/k0e4q-9pt77", "type": "article", "title": "Clock-line photoassociation of strongly bound dimers in a magic-wavelength lattice", "author": [ { "family_name": "Bettermann", "given_name": "O.", "clpid": "Bettermann-O" }, { "family_name": "Darkwah Oppong", "given_name": "N.", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Pasqualetti", "given_name": "G.", "clpid": "Pasqualetti-G" }, { "family_name": "Riegger", "given_name": "L.", "clpid": "Riegger-L" }, { "family_name": "Bloch", "given_name": "I.", "orcid": "0000-0002-0679-4759", "clpid": "Bloch-Immanuel" }, { "family_name": "F\u00f6lling", "given_name": "S.", "orcid": "0000-0002-6951-3651", "clpid": "F\u00f6lling-Simon" } ], "abstract": "We report on the direct optical production and spectroscopy of ¹\ud835\udc46\u2080−³\ud835\udc43\u2080 molecules with large binding energy using the clock transition of ¹\u2077¹\u2062Yb, and on the observation of the associated orbital Feshbach resonance near 1300G. We measure the magnetic field dependence of the closed-channel dimer and of the open-channel pair state energy via clock-line spectroscopy in a deep optical lattice. In addition, we show that the free-to-bound transition into the dimer can be made first-order insensitive to the trap depth by the choice of lattice wavelength. Finally, we determine the fundamental intra- and interorbital scattering lengths and probe the stability of the corresponding pair states, finding long lifetimes in both interorbital interaction channels. These results are promising both for molecular clocks and for the preparation of strongly interacting multiorbital Fermi gases.
", "doi": "10.1103/physreva.108.l041302", "issn": "2469-9926", "publisher": "American Physical Society", "publication": "Physical Review A", "publication_date": "2023-10", "series_number": "4", "volume": "108", "issue": "4", "pages": "L041302" }, { "id": "authors:pehff-2qc34", "collection": "authors", "collection_id": "pehff-2qc34", "cite_using_url": "https://authors.library.caltech.edu/records/pehff-2qc34", "type": "article", "title": "Realizing spin squeezing with Rydberg interactions in an optical clock", "author": [ { "family_name": "Eckner", "given_name": "William J.", "orcid": "0000-0003-0833-7137", "clpid": "Eckner-William-J" }, { "family_name": "Darkwah Oppong", "given_name": "Nelson", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Cao", "given_name": "Alec", "orcid": "0000-0002-6111-1375", "clpid": "Cao-Alec" }, { "family_name": "Young", "given_name": "Aaron W.", "orcid": "0000-0002-3490-4046", "clpid": "Young-Aaron-W" }, { "family_name": "Milner", "given_name": "William R.", "orcid": "0000-0003-0510-0775", "clpid": "Milner-William-R" }, { "family_name": "Robinson", "given_name": "John M.", "clpid": "Robinson-John-M" }, { "family_name": "Ye", "given_name": "Jun", "orcid": "0000-0003-0076-2112", "clpid": "Ye-Jun" }, { "family_name": "Kaufman", "given_name": "Adam M.", "orcid": "0000-0003-4956-5814", "clpid": "Kaufman-Adam-M" } ], "abstract": "Neutral-atom arrays trapped in optical potentials are a powerful platform for studying quantum physics, combining precise single-particle control and detection with a range of tunable entangling interactions1,2,3. For example, these capabilities have been leveraged for state-of-the-art frequency metrology4,5 as well as microscopic studies of entangled many-particle states6,7,8,9,10,11. Here we combine these applications to realize spin squeezing—a widely studied operation for producing metrologically useful entanglement—in an optical atomic clock based on a programmable array of interacting optical qubits. In this demonstration of Rydberg-mediated squeezing with a neutral-atom optical clock, we generate states that have almost four decibels of metrological gain. In addition, we perform a synchronous frequency comparison between independent squeezed states and observe a fractional-frequency stability of 1.087(1) × 10−15 at one-second averaging time, which is 1.94(1) decibels below the standard quantum limit and reaches a fractional precision at the 10−17 level during a half-hour measurement. We further leverage the programmable control afforded by optical tweezer arrays to apply local phase shifts to explore spin squeezing in measurements that operate beyond the relative coherence time with the optical local oscillator. The realization of this spin-squeezing protocol in a programmable atom-array clock will enable a wide range of quantum-information-inspired techniques for optimal phase estimation and Heisenberg-limited optical atomic clocks12,13,14,15,16.
\nConstraints in the dynamics of quantum many-body systems can dramatically alter transport properties and relaxation timescales even in the absence of static disorder. Here, we report on the observation of such constrained dynamics arising from the distinct mobility of two species in the one-dimensional mass-imbalanced Fermi-Hubbard model, realized with ultracold ytterbium atoms in a state-dependent optical lattice. By displacing the trap potential and monitoring the subsequent dynamical response of the system, we identify suppressed transport and slow relaxation with a strong dependence on the mass imbalance and interspecies interaction strength, consistent with eventual thermalization for long times. Our observations demonstrate the potential for quantum simulators to provide insights into unconventional relaxation dynamics arising from constraints.
", "doi": "10.1103/physrevx.12.031026", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2022-07", "series_number": "3", "volume": "12", "issue": "3", "pages": "031026" }, { "id": "authors:gf1f2-cfw76", "collection": "authors", "collection_id": "gf1f2-cfw76", "cite_using_url": "https://authors.library.caltech.edu/records/gf1f2-cfw76", "type": "article", "title": "Quasiparticle Lifetime of the Repulsive Fermi Polaron", "author": [ { "family_name": "Adlong", "given_name": "Haydn S.", "orcid": "0000-0002-7782-3975", "clpid": "Adlong-Haydn-S" }, { "family_name": "Liu", "given_name": "Weizhe Edward", "orcid": "0000-0003-1019-5297", "clpid": "Liu-Weizhe-Edward" }, { "family_name": "Scazza", "given_name": "Francesco", "orcid": "0000-0001-5527-1068", "clpid": "Scazza-Francesco" }, { "family_name": "Zaccanti", "given_name": "Matteo", "orcid": "0000-0001-6214-4921", "clpid": "Zaccanti-Matteo" }, { "family_name": "Darkwah Oppong", "given_name": "Nelson", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "F\u00f6lling", "given_name": "Simon", "orcid": "0000-0002-6951-3651", "clpid": "F\u00f6lling-Simon" }, { "family_name": "Parish", "given_name": "Meera M.", "orcid": "0000-0001-8705-0171", "clpid": "Parish-Meera-M" }, { "family_name": "Levinsen", "given_name": "Jesper", "orcid": "0000-0002-2010-3512", "clpid": "Levinsen-Jesper" } ], "abstract": "We investigate the metastable repulsive branch of a mobile impurity coupled to a degenerate Fermi gas via short-range interactions. We show that the quasiparticle lifetime of this repulsive Fermi polaron can be experimentally probed by driving Rabi oscillations between weakly and strongly interacting impurity states. Using a time-dependent variational approach, we find that we can accurately model the impurity Rabi oscillations that were recently measured for repulsive Fermi polarons in both two and three dimensions. Crucially, our theoretical description does not include relaxation processes to the lower-lying attractive branch. Thus, the theory-experiment agreement demonstrates that the quasiparticle lifetime is dominated by many-body dephasing within the upper repulsive branch rather than by relaxation from the upper branch itself. Our findings shed light on recent experimental observations of persistent repulsive correlations, and have important consequences for the nature and stability of the strongly repulsive Fermi gas.
", "doi": "10.1103/physrevlett.125.133401", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2020-09-25", "series_number": "13", "volume": "125", "issue": "13", "pages": "133401" }, { "id": "authors:0zmj9-30026", "collection": "authors", "collection_id": "0zmj9-30026", "cite_using_url": "https://authors.library.caltech.edu/records/0zmj9-30026", "type": "article", "title": "Observation of Coherent Multiorbital Polarons in a Two-Dimensional Fermi Gas", "author": [ { "family_name": "Darkwah Oppong", "given_name": "N.", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "Riegger", "given_name": "L.", "clpid": "Riegger-L" }, { "family_name": "Bettermann", "given_name": "O.", "clpid": "Bettermann-O" }, { "family_name": "H\u00f6fer", "given_name": "M.", "clpid": "H\u00f6fer-M" }, { "family_name": "Levinsen", "given_name": "J.", "orcid": "0000-0002-2010-3512", "clpid": "Levinsen-Jesper" }, { "family_name": "Parish", "given_name": "M.\u2009M.", "orcid": "0000-0001-8705-0171", "clpid": "Parish-Meera-M" }, { "family_name": "Bloch", "given_name": "I.", "orcid": "0000-0002-0679-4759", "clpid": "Bloch-Immanuel" }, { "family_name": "F\u00f6lling", "given_name": "S.", "orcid": "0000-0002-6951-3651", "clpid": "F\u00f6lling-Simon" } ], "abstract": "We report on the experimental observation of multiorbital polarons in a two-dimensional Fermi gas of ¹\u2077³Yb atoms formed by mobile impurities in the metastable ³\ud835\udc43\u2080 orbital and a Fermi sea in the ground-state ¹\ud835\udc46\u2080 orbital. We spectroscopically probe the energies of attractive and repulsive polarons close to an orbital Feshbach resonance and characterize their coherence by measuring the quasiparticle residue. For all probed interaction parameters, the repulsive polaron is a long-lived quasiparticle with a decay rate more than 2 orders of magnitude below its energy. We formulate a many-body theory, which accurately treats the interorbital interactions in two dimensions and agrees well with the experimental results. Our work paves the way for the investigation of many-body physics in multiorbital ultracold Fermi gases.
", "doi": "10.1103/physrevlett.122.193604", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2019-05-17", "series_number": "19", "volume": "122", "issue": "19", "pages": "193604" }, { "id": "authors:p8sp8-zf740", "collection": "authors", "collection_id": "p8sp8-zf740", "cite_using_url": "https://authors.library.caltech.edu/records/p8sp8-zf740", "type": "article", "title": "Localized Magnetic Moments with Tunable Spin Exchange in a Gas of Ultracold Fermions", "author": [ { "family_name": "Riegger", "given_name": "L.", "clpid": "Riegger-L" }, { "family_name": "Darkwah Oppong", "given_name": "N.", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "H\u00f6fer", "given_name": "M.", "clpid": "H\u00f6fer-M" }, { "family_name": "Fernandes", "given_name": "D.\u2009R.", "clpid": "Fernandes-D-R" }, { "family_name": "Bloch", "given_name": "I.", "orcid": "0000-0002-0679-4759", "clpid": "Bloch-Immanuel" }, { "family_name": "F\u00f6lling", "given_name": "S.", "orcid": "0000-0002-6951-3651", "clpid": "F\u00f6lling-Simon" } ], "abstract": "We report on the experimental realization of a state-dependent lattice for a two-orbital fermionic quantum gas with strong interorbital spin exchange. In our state-dependent lattice, the ground and metastable excited electronic states of ¹\u2077³Yb take the roles of itinerant and localized magnetic moments, respectively. Repulsive on-site interactions in conjunction with the tunnel mobility lead to spin exchange between mobile and localized particles, modeling the coupling term in the well-known Kondo Hamiltonian. In addition, we find that this exchange process can be tuned resonantly by varying the on-site confinement. We attribute this to a resonant coupling to center-of-mass excited bound states of one interorbital scattering channel.
", "doi": "10.1103/physrevlett.120.143601", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2018-04-06", "series_number": "14", "volume": "120", "issue": "14", "pages": "143601" }, { "id": "authors:q0mb1-qd515", "collection": "authors", "collection_id": "q0mb1-qd515", "cite_using_url": "https://authors.library.caltech.edu/records/q0mb1-qd515", "type": "article", "title": "A Fermi-degenerate three-dimensional optical lattice clock", "author": [ { "family_name": "Campbell", "given_name": "S. L.", "orcid": "0000-0002-7335-8391" }, { "family_name": "Hutson", "given_name": "R. B.", "orcid": "0000-0002-2243-5625" }, { "family_name": "Marti", "given_name": "G. E." }, { "family_name": "Goban", "given_name": "A.", "orcid": "0000-0003-0027-1399" }, { "family_name": "Darkwah Oppong", "given_name": "N.", "orcid": "0000-0002-2114-6848", "clpid": "Darkwah-Oppong-N" }, { "family_name": "McNally", "given_name": "R. L." }, { "family_name": "Sonderhouse", "given_name": "L.", "orcid": "0000-0002-6814-5391" }, { "family_name": "Robinson", "given_name": "J. M." }, { "family_name": "Zhang", "given_name": "W.", "orcid": "0000-0003-2065-2535" }, { "family_name": "Bloom", "given_name": "B. J.", "orcid": "0000-0001-6831-0601" }, { "family_name": "Ye", "given_name": "J.", "orcid": "0000-0003-3702-7445" } ], "abstract": "