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1. Rydberg mediated entanglement in a two-dimensional neutral atom qubit array

   Graham, TM ; Kwon, M. ; Grinkemeyer, B. ; Marra, Z. ; Jiang, X ; Lichtman, M.T. ; Sun, Y. ; Ebert, M. ; and M. Saffman, M. ( August 2019 , ArXiv.org)

   We demonstrate high fidelity two-qubit Rydberg blockade and entanglement in a two-dimensional qubit array. The qubit array is defined by a grid of blue detuned lines of light with 121 sites for trapping atomic qubits. Improved experimental methods have increased the observed Bell state fidelity to FBell = 0.86(2). Accounting for errors in state preparation and measurement (SPAM) we infer a fidelity of F−SPAM Bell = 0.89. Including errors in single qubit operations we infer that the Rydberg mediated CZ gate has a fidelity of F−SPAM CZ= 0.91. Comparison with a detailed error model shows that further improvement in fidelity will require colder atoms and lasers with reduced noise.
2. Quantum information with Rydberg excited atoms1

   Saffman, M. ( May 2019 , DAMOP 2019)

   Optically trapped neutral atoms are one of several leading approaches for scalable quantum information processing. When prepared in electronic ground states in deep optical lattices atomic qubits are weakly interacting with long coherence times. Excitation to Rydberg states turns on strong interactions which enable fast gates and entanglement generation. I will present quantum logic experiments with a 2D array of blue detuned lines that traps more than 100 Cesium atom qubits. The array is randomly loaded from a MOT and an optical tweezer steered by a 2D acousto-optic deflector is used to ll subregions of the array. Progress towards high fidelity entangling gates based on Rydberg excitation lasers with lower noise, and optimized optical polarization and magnetic eld settings will be shown.
3. A reconfigurable blue-detuned lattice for neutral atom quantum computing

   Graham, Trent ; Poole, Cody ; Xiaoyu, Jiang ; Marra, Alphonse ; Grinkemeyer, Brandon ; Hickman, Garrett ; Cherek, Josh ; Ebert, Matthew ; Saffman, Mark ( May 2019 , 50th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting)

   We present recent progress towards building a neutral atom quantum computer. We use a new design for a blue-detuned optical lattice to trap single Cs atoms. The lattice is created using a combination of diffractive elements and acousto-optic deflectors (AODs) which give a reconfigurable set of cross-hatched lines. By using AODs, we can vary the number of traps and size of the trapping regions as well as eliminate extraneous traps in Talbot planes. Since this trap uses blue-detuned light, it traps both ground state atoms and atoms excited to the Rydberg state; moreover, by tuning the size of the trapping region, we can make the traps “magic” for a selected Rydberg state. We use an optical tweezer beam for atom rearrangement. When loading atoms into the array, trap sites randomly contain zero or one atoms. Atoms are then moved between different trapping sites using a red-detuned optical tweezer. Optimal atom rearrangement is calculated using the “Hungarian Method”. These rearrangement techniques can be used to create defect-free sub-lattices. Lattice atoms can also be used as a reservoir for a set of selected sites. This allows quick replacement of atoms, and increased data rate, without reloading from a MOT.
4. A reconfigurable blue-detuned lattice for neutral atom quantum computing

   GRAHAM, T. ; POOLE, C ; JIANG, X ; MARRA, Z ; GRINKEMEYER, B ; HICKMAN, G ; CHEREK, J ; EBERT, M ; SAFFMAN, M. ( May 2019 , DAMOP 2019)

   We present recent progress towards building a neutral atom quantum computer. We use a new design for a blue-detuned optical lattice to trap single Cs atoms. The lattice is created using a combination of diffractive elements and acousto-optic deflectors (AODs) which give a reconfigurable set of cross-hatched lines. By using AODs, we can vary the number of traps and size of the trapping regions as well as eliminate extraneous traps in Talbot planes. Since this trap uses blue-detuned light, it traps both ground state atoms and atoms excited to the Rydberg state; moreover, by tuning the size of the trapping region, we can make the traps “magic” for a selected Rydberg state. We use an optical tweezer beam for atom rearrangement. When loading atoms into the array, trap sites randomly contain zero or one atoms. Atoms are then moved between different trapping sites using a red-detuned optical tweezer. Optimal atom rearrangement is calculated using the “Hungarian Method”. These rearrangement techniques can be used to create defect-free sub-lattices. Lattice atoms can also be used as a reservoir for a set of selected sites. This allows quick replacement of atoms, and increased data rate, without reloading from a MOT.
5. Long-lived Bell states in an array of optical clock qubits

   https://doi.org/10.48550/arXiv.2111.14653  

   Schine, N. ; Young, A.W. ; Eckner, W.J. ; Martin, M. J. ; Kaufman, A. M. ( July 2022 , ArXivorg)

   The generation of long-lived entanglement on an optical clock transition is a key requirement to unlocking the promise of quantum metrology. Arrays of neutral atoms constitute a capable quantum platform for accessing such physics, where Rydberg-based interactions may generate entanglement between individually controlled and resolved atoms. To this end, we leverage the programmable state preparation afforded by optical tweezers along with the efficient strong confinement of a 3d optical lattice to prepare an ensemble of strontium atom pairs in their motional ground state. We engineer global single-qubit gates on the optical clock transition and two-qubit entangling gates via adiabatic Rydberg dressing, enabling the generation of Bell states, |ψ⟩=12√(|gg⟩+i|ee⟩), with a fidelity of F=92.8(2.0)%. For use in quantum metrology, it is furthermore critical that the resulting entanglement be long lived; we find that the coherence of the Bell state has a lifetime of τbc=4.2(6) s via parity correlations and simultaneous comparisons between entangled and unentangled ensembles. Such Bell states can be useful for enhancing metrological stability and bandwidth. Further rearrangement of hundreds of atoms into arbitrary configurations using optical tweezers will enable implementation of many-qubit gates and cluster state generation, as well as explorations of the transverse field Ising model andmore »Hubbard models with entangled or finite-range-interacting tunnellers.« less