Many-body quantum systems can exhibit a striking degree of symmetry unparallelled in their classical counterparts. In real materials SU(N) symmetry is an idealization, but this symmetry is pristinely realized in fully controllable ultracold alkaline-earth atomic gases. Here, we study an SU(N)-symmetric Fermi liquid of 87Sr atoms, where N can be tuned to be as large as 10. In the deeply degenerate regime, we show through precise measurements of density fluctuations and expansion dynamics that the large N of spin states under SU(N) symmetry leads to pronounced interaction effects in a system with a nominally negligible interaction parameter. Accounting for these effects, we demonstrate thermometry accurate to 1% of the Fermi energy. We also demonstrate record speed for preparing degenerate Fermi seas enabled by the SU(N)-symmetric interactions, reaching T/TF = 0.22 with 10 nuclear spin states in 0.6 s working with a laser-cooled sample. This, along with the introduction of a new spin polarizing method, enables the operation of a three-dimensional optical lattice clock in the band insulating regime. Ultracold alkaline-earth fermionic atoms with large number of nuclear spin states possess SU(N) symmetry. That deeply affects their interaction properties, and allows a Fermi gas of these atoms to be cooled quickly to the quantum degenerate regime.

Last. Gyu-Boong Jo(HKUST: Hong Kong University of Science and Technology)H-Index: 16

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Quantum simulations show that bosonization---bosonlike behavior emerging from an ensemble of fermions---can occur in 3D systems, a hypothesis that until now has been unresolved.

#1Chengdong He(HKUST: Hong Kong University of Science and Technology)H-Index: 6

#2Zejian Ren(HKUST: Hong Kong University of Science and Technology)H-Index: 5

Last. Gyu-Boong Jo(HKUST: Hong Kong University of Science and Technology)H-Index: 16

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The authors realize a two-dimensional gas of SU(N) fermions, and evaluate collective mode frequencies in the system. It includes the measurements of breathing and quadrupole mode frequencies, the latter of which decreases for larger spin component N due to the enhanced interaction. The paper provides a mean-field theory in good agreement with the observation. The dimensional evolution of collective excitations from two to three dimensions and the damping rate of collective modes provides an insi...

#1Victoria Xu(University of California, Berkeley)H-Index: 4

#2Matt Jaffe(University of California, Berkeley)H-Index: 9

Last. Holger Müller(University of California, Berkeley)H-Index: 39

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Atom interferometers are powerful tools for both measurements in fundamental physics and inertial sensing applications. Their performance, however, has been limited by the available interrogation time of freely falling atoms in a gravitational field. By suspending the spatially separated atomic wave packets in a lattice formed by the mode of an optical cavity, we realize an interrogation time of 20 seconds. Our approach allows gravitational potentials to be measured by holding, rather than dropp...

#1Eric Oelker(NIST: National Institute of Standards and Technology)H-Index: 67

#2Ross B. Hutson(NIST: National Institute of Standards and Technology)H-Index: 10

Last. Jun Ye(NIST: National Institute of Standards and Technology)H-Index: 126

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Optical atomic clocks require local oscillators with exceptional optical coherence owing to the challenge of performing spectroscopy on their ultranarrow-linewidth clock transitions. Advances in laser stabilization have thus enabled rapid progress in clock precision. A new class of ultrastable lasers based on cryogenic silicon reference cavities has recently demonstrated the longest optical coherence times to date. Here we utilize such a local oscillator with two strontium (Sr) optical lattice c...

#1Ross B. Hutson(CU: University of Colorado Boulder)H-Index: 10

#2Akihisa Goban(CU: University of Colorado Boulder)H-Index: 17

Last. Jun Ye(CU: University of Colorado Boulder)H-Index: 126

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We investigate the effects of stimulated scattering of optical lattice photons on atomic coherence times in a state-of-the art {}^{87}\mathrm{Sr}optical lattice clock. Such scattering processes are found to limit the achievable coherence times to less than 10 s, significantly shorter than the predicted 145(40) s lifetime of {}^{87}\mathrm{Sr}s excited clock state. We suggest that shallow, state-independent optical lattices with increased lattice constants can give rise to sufficiently smal...

Questioning basic assumptions about the structure of space and time has greatly enhanced our understanding of nature. State-of-the-art atomic clocks1–3 make it possible to precisely test fundamental symmetry properties of spacetime and search for physics beyond the standard model at low energies of just a few electronvolts4. Modern tests of Einstein’s theory of relativity try to measure so-far-undetected violations of Lorentz symmetry5; accurately comparing the frequencies of optical clocks is a...

Optical atomic clocks require local oscillators with exceptional optical coherence owing to the challenge of performing spectroscopy on their ultranarrow-linewidth clock transitions. Advances in laser stabilization have thus enabled rapid progress in clock precision. A new class of ultrastable lasers based on cryogenic silicon reference cavities has recently demonstrated the longest optical coherence times to date. Here we utilize such a local oscillator with two strontium (Sr) optical lattice c...

Last. Andrew D. Ludlow(CU: University of Colorado Boulder)H-Index: 39

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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 referen...

Large-spin cold atomic systems can exhibit unique phenomena that do not appear in spin-1/2 systems. We report the observation of nearest-neighbor antiferromagnetic spin correlations of a Fermi gas with SU(\mathcal{N} symmetry trapped in an optical lattice. The precise control of the spin degrees of freedom provided by an optical pumping technique enables us a straightforward comparison between the cases of SU(2) and SU(4). Our important finding is that the antiferromagnetic correlation is enh...

#1Akihisa Goban(CU: University of Colorado Boulder)H-Index: 17

#2Ross B. Hutson(CU: University of Colorado Boulder)H-Index: 10

Last. Jun Ye(CU: University of Colorado Boulder)H-Index: 126

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Alkaline-earth atoms have metastable ‘clock’ states with minute-long optical lifetimes, high-spin nuclei and SU(N)-symmetric interactions, making them powerful platforms for atomic clocks1, quantum information processing2 and quantum simulation3. Few-particle systems of such atoms provide opportunities to observe the emergence of complex many-body phenomena with increasing system size4. Multi-body interactions among particles are emergent phenomena, which cannot be broken down into sums over und...

We study multilevel fermions in an optical lattice described by the Hubbard model with on site SU(n-symmetric interactions. We show that in an appropriate parameter regime this system can be mapped onto a spin model with all-to-all SU(n-symmetric couplings. Raman pulses that address internal spin states modify the atomic dispersion relation and induce spin-orbit coupling, which can act as a synthetic inhomogeneous magnetic field that competes with the SU(n exchange interactions. We inve...

Last. Hong Chang(CAS: Chinese Academy of Sciences)H-Index: 9

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The quantum system under periodical modulation is the simplest path to understand the quantum non-equilibrium system, because it can be well described by the effective static Floquet Hamiltonian. Under the stroboscopic measurement, the initial phase is usually irrelevant. However, if two uncorrelated parameters are modulated, their relative phase can not be gauged out, so that the physics can be dramatically changed. Here, we simultaneously modulate the frequency of the lattice laser and the Rab...

We investigate a species selective cooling process of a trapped \mathrm{SU}(N)Fermi gas using entropy redistribution during adiabatic loading of an optical lattice. Using high-temperature expansion of the Hubbard model, we show that when a subset N_A < Nof the single-atom levels experiences a stronger trapping potential in a certain region of space, the dimple, it leads to improvement in cooling as compared to a \mathrm{SU}(N_A)Fermi gas only. We show that optimal performance is achieve...

Dipole-dipole interactions lead to frequency shifts that are expected to limit the performance of next-generation atomic clocks. In this work, we compute dipolar frequency shifts accounting for the intrinsic atomic multilevel structure in standard Ramsey spectroscopy. When interrogating the transitions featuring the smallest Clebsch-Gordan coefficients, we find that a simplified two-level treatment becomes inappropriate, even in the presence of large Zeeman shifts. For these cases, we show a net...

Synchronization is a dynamical phenomenon found in complex systems ranging from biological systems to human society and is characterized by the constituents parts of a system locking their motion so that they have the same phase and frequency. Recent intense efforts have focused on understanding synchronization in quantum systems without clear semi-classical limits but no comprehensive theory providing a systematic basis for the underlying physical mechanisms has yet been found. Through a comple...

Spontaneous decay of an excited atomic state is a fundamental process that originates from the interaction between matter and vacuum modes of the electromagnetic field. The rate of decay can thus be engineered by modifying the density of final states of the joint atom-photon system. Imposing suitable boundary conditions on the electromagnetic field has been shown to alter the density of vacuum modes near the atomic transition, resulting in modified atomic decay rates. Here we report the first ex...

We demonstrate photoassociation (PA) of ultracold fermionic ^{87}r atoms. The binding energies of a series of molecular states on the ^1\Sigma^+_u5s^2\,^1_0+5s5p\,^1_1molecular potential are fit with the semiclassical LeRoy-Bernstein model, and PA resonance strengths are compared to predictions based on the known ^1_0+^1_0ground state potential. Similar measurements and analysis were performed for the bosonic isotopes ^{84}r and ^{86}r, allowing a combined analysis ...

Last. Gyu-Boong Jo(HKUST: Hong Kong University of Science and Technology)H-Index: 16

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Quantum simulations show that bosonization---bosonlike behavior emerging from an ensemble of fermions---can occur in 3D systems, a hypothesis that until now has been unresolved.