Session A19: Quantum Simulation and Computation with Neutral Atom Optical Tweezer Arrays

Building Single Molecules in Optical Tweezers

Ultracold polar molecules are sought-after for a range of new possibilities from studying ultracold chemical reactions to building quantum simulators and computers. My group develops techniques to assemble single molecules atom-by-atom with full internal and motional state control. Starting with ground-state cooled single atoms, we magneto-associate a single NaCs molecule near a newly identified s-wave Feshbach resonance. Furthermore, by preparing a constituent atom with one motional excitation, we produce a p-wave Feshbach molecule. With an additional Raman transfer step of molecules from Feshbach state to the rovibronic ground state, we foresee these single molecules as valuable resources for quantum simulation and quantum computation due to their rich internal degrees of freedom and strong tunable inter-molecular coupling.   

Atom arrays of ultracold strontium: new tools for many-body physics and metrology

The development of microscopic detection of ensembles of neutral atoms has transformed our ability to study complex many-body systems. Techniques like quantum gas microscopy and optical tweezer arrays grant a unique single-particle-resolved perspective on solid-state analogs and idealized quantum spin models, as well as detection capabilities of quantities like entanglement. In this talk, I will describe our group's progress towards developing these tools for a new atomic species, strontium. In doing so, we establish new prospects enabled by the rich internal degrees-of-freedom associated with alkaline-earth atoms. I will report on our recent results in which we apply our platform to optical atomic clocks, a new application of optical tweezer arrays which indicates a number of strengths for metrology. I will then describe our progress towards engineering entanglement on an optical clock transition, as well as new strategies to coherently control samples with 100s of atoms.   

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

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) and single qubit operations
we infer that a Bell state created with the Rydberg mediated CZ gate has a fidelity of 0.89. Comparison with
a detailed error model based on quantum process matrices indicates that finite atom temperature
and laser noise are the dominant error sources contributing to the observed gate infidelity.   

Quantum Science with Ytterbium Rydberg Atoms in Optical Tweezer Arrays

Engineering Rydberg-mediated interactions in arrays of neutral atom qubits is a leading platform for quantum computing and quantum simulation architectures. The advantages of this experimental platform are derived from the strong nature of Rydberg interactions coupled with highly controllable optical tweezer arrays. To date, most neutral atom array experiments utilize alkali atoms, however alkaline-earth-like atoms offer many advantages including extremely long coherence times for nuclear spins in the J = 0 electronic ground state and narrow optical transitions for use in efficient laser-cooling, metrology and precision measurement. Our experimental approach is to utilize laser-cooled neutral ytterbium (Yb) atoms trapped in optical tweezer arrays. We use the narrow intercombination line, ¹S₀ - ³P₁, for cooling and imaging atoms in magic-wavelength (532 nm) optical tweezers and achieve very high atom detection fidelity [1]. An additional advantage of Yb is the ability to stably trap Rydberg states of the atom by leveraging the Yb⁺ ion core polarizability for trapping in the optical tweezer. Here we maintain trapping of the Rydberg atom at high n states thus extending the lifetime for interactions. The expanded interaction time has important implications for quantum computing and simulation with strongly interacting Rydberg atoms. These attributes make Yb atoms in optical tweezers an attractive platform for a wide variety of applications in quantum information science.

[1] S. Saskin et. al. Phys. Rev. Lett. 122, 143002 (2019)   

Quantum Science with Tweezer Arrays

Recently cold atoms in optical tweezer arrays have emerged as a versatile platform for quantum science experiments. I will review some of these developments, specifically, atom-by-atom assembly [1] as a fast and simple method to generate defect-free atomic arrays and Rydberg-based quantum simulation of spin models. While already reaching competitive results, these systems are still in their infancy and limitations in coherence, detection fidelity, and scalability remain. I will outline how we can improve on these issues and at the same time open new avenues in quantum metrology by using alkaline earth atoms, followed by an overview of recent results: 1) A record in imaging-fidelity for neutral atoms and demonstration of narrow-line cooling in tweezers [2,3]. 2) High-fidelity Rydberg excitation from a clock state, including a record in entanglement-fidelity for two neutral atoms [4]. 3) Demonstration of an optical clock with single-atom detection in tweezer arrays [5].

[1] Endres et al., Science 354, 1024 (2016)
[2] Covey et. al, Phys. Rev. Lett. 122, 173201 (2019)
[3] Cooper et al., Phys. Rev. X 8, 041055 (2018)
[4] Madjarov*, Covey*, et al., arXiv:2001.04455 (2020)
[5] Madjarov et al., Phys. Rev. X 9, 041052 (2019)