Spin-resolved microscopy of 87 Sr SU(N) Fermi-Hubbard systems

Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: We're looking at the paper: "Spin-resolved microscopy of 87 Sr SU(N) Fermi-Hubbard systems".

Mira: Here's the gist of the paper. The gist The realization of a quantum-gas microscope for fermionic 87Sr establishes it as a powerful approach to study exotic magnetism in the SU(N) Fermi-Hubbard model and provides a new detection tool for studies in quantum simulation, computation, and metrology System Realization The research demonstrates the realization of a quantum-gas microscope for fermionic 87Sr using a narrow intercombination line at 689 nm for cooling and imaging This scheme enables spin-resolved single-atom detection by implementing a spin-selective optical pumping protocol to determine the occupation of each of the 10 spin states in a single experimental realization The system realizes the two-dimensional SU(N) Fermi-Hubbard model, with N (up to 10) controlled by the number of populated Zeeman sublevels This is achieved by loading the atomic cloud into a four-fold interfering square lattice and using a clock-magic wavelength of 813.4 nm for the imaging potential Imaging and Detection Protocol The imaging protocol involves sequential and independent site-resolved detection of all 10 spin states of strontium in a single experimental run The imaging beam resonantly addresses the 1S0 9/2, −9/2⟩ → 3P1 11/2, −11/2⟩ cycling transition while all other transitions remain off-resonant The bias magnetic field of B ≈ 20 G results in a Zeeman splitting of approximately 8 MHz, ensuring the independent addressing of a single spin state Consecutive fluorescence images allow for the reconstruction of occupation matrices, and the pinning fidelity Fpin was found to be 92.5(7)% Spin Manipulation and Fidelity Additional spin manipulation tools are required to measure all other spin states, with optical pumping being a common option Optical pumping fidelity FOP,1 was found to be 95.6(8)% when transferring atoms from the stretched state to the mF = −9/2 state For the central states, a higher optical-pumping fidelity FOP,2 of 99.8(1)% was estimated when using an increasing number of pulses p≥3 Benchmarking and Correlators The protocol is benchmarked by studying the Larmor precession dynamics of the ground-state nuclear spin, F = 9/2 Coherent spin oscillations with revivals of the mF = −9/2 state were observed over a period T = 40.16(6) ms, yielding a magnetic field of By = 135.0(2) mG The analysis isolates the last remaining source of infidelity as vacuum-induced losses, which were measured to be Lvac = 0.95(3)% per spin-readout cycle The results confirm that all processes underlying the detection protocol are well controlled, providing a clear route to further increase the pinning fidelity, which already exceeds 92% Future work should focus on microscopic characterization of SU(N) degenerate Fermi gases with a tunable number of components and the preparation and site-resolved study of SU(N) fermionic Mott insulators The technique may also be applied to optical lattice clocks to enable novel erasure-conversion strategies and improve coherence times The realization of a quantum-gas microscope for fermionic 87Sr establishes it as a powerful approach to study exotic magnetism in the SU(N) Fermi-Hubbard model and provides a new detection tool for studies in quantum simulation, computation, and metrology The system realizes the two-dimensional SU(N) Fermi-Hubbard model, with N (up to 10) controlled by the number of populated Zeeman sublevels The imaging protocol involves sequential and independent site-resolved detection of all 10 spin states of strontium in a single experimental run Spin manipulation tools like optical pumping allow for the retrieval of atomic populations, with optical pumping fidelity FOP,1 being 95.6(8)% and FOP,2 being 99.8(1)% Benchmarking through Larmor precession dynamics confirmed the protocol's robustness, isolating vacuum losses as the dominant infidelity source at 0.95(3)% per cycle This capability is essential for revealing the magnetic properties of the SU(N) Fermi-Hubbard model by accessing spin-spin correlators The scheme provides a sensitive diagnostic for identifying spurious processes like spin depolarization, which is attributed to trap-induced off-resonant Raman scattering This work demonstrates the ability to probe SU(N) quantum magnetism and offers a versatile detection method for quantum computing schemes based on the nuclear spin of 87Sr How it works 1.

Kai: The system is prepared by laser cooling 87Sr atoms to temperatures on the order of 1 µK using a narrow-line MOT operating on the 1S0 → 3P1 transition at 689 nm These atoms are then loaded into a crossed optical dipole trap and transferred to an optical lattice potential with depths of 55 µK and 80 µK 2.

Mira: Spin-resolved imaging is achieved by resonantly addressing the 1S0 9/2, −9/2⟩ → 3P1 11/2, −11/2⟩ transition using a bias magnetic field of B ≈ 20 G This allows the imaging process to be inherently spin-resolved by exploiting the narrow linewidth of the imaging transition 3.

Paper summary: Kai: So this paper is about realizing a quantum-gas microscope for fermionic 87Sr <ref:2603.05478#pg1,a quantum-gas microscope for fermionic 87Sr>. The main idea is that alkaline-earth(-like) fermions can extend the spin-one/two paradigm to higher symmetries and give access to SU(N) Hubbard models, which have really rich phase diagrams waiting to be unveiled <ref:2603.05478#pg1,access to SU(N) Hubbard models>.

Mira: They are focusing on the competition between interactions, SU(two) magnetism, and doping in these systems <ref:2603.05478#pg1,competition between interactions, SU(2) magnetism, and doping>. The paper reports that they've managed this realization for 87Sr specifically <ref:2603.05478#pg1>.

Lev: And the system they realize is the two-dimensional SU(N) Fermi-Hubbard model, with N up to ten controlled by how many Zeeman sublevels you populate, which is what makes it so interesting <ref:2603.05478#pg2,SU(N) Fermi-Hubbard model>.

Kai: The imaging scheme itself relies on cooling and fluorescence on that narrow intercombination line at six hundred eighty-nine nm to enable spin-resolved single-atom detection <ref:2603.05478#pg1,narrow intercombination line at 689 nm>. They use a spin-selective optical pumping protocol to determine the occupation of each of the ten spin states in a single experimental realization.

Mira: It matters because it gives us this crucial capability for probing site-resolved magnetic correlations, which is what you need when you're trying to understand how magnetism works on a lattice.

Lev: They also use the measured detection fidelities to demonstrate its capability to resolve those many-body spin correlations by running numerical simulations of SU(N) Fermi-Hubbard chains.

Conclusion: Kai: So the title, "Spin-resolved microscopy of eighty-seven Sr SU(N) Fermi-Hubbard systems," points directly to the core achievement: they built a tool to see the magnetic phases of these complex models using strontium atoms <ref:2603.05478#pg1,SU(N) Fermi-Hubbard systems>.

Mira: It really means they've taken a theoretical interest in SU(N) quantum systems and made it experimentally accessible through this specific microscopy technique.

Lev: For me, what this means is that we now have a new detection tool for quantum simulation, computation, and metrology because of how sensitive the measurements are described.

Kai: Exactly. It's not just about seeing one atom; it’s about mapping out the entire spin-resolved structure of the system in a single run. It lets us probe things that were previously only theoretical constructs.

Mira: And they have shown that this approach works for SU(N) models up to N=ten with 87Sr, which is a significant step in realizing these high symmetry systems experimentally <ref:2603.05478#pg2>.

Lev: The limitation they point out is that they still need to focus on microscopic characterization of SU(N) degenerate Fermi gases and preparing site-resolved studies of SU(N) fermionic Mott insulators.

Kai: So the path forward involves using this microscopy to study those specific insulating states and understanding how those high symmetry systems behave under different conditions.