Let me tell you what I have achieved in HoodLAb. The lithium–cesium program in our lab has progressed through three technical milestones: (1) the first optical-tweezer trapping and high-fidelity imaging of a single ⁶Li atom, (2) development of a unified theoretical model that clarifies sub-Doppler cooling in tweezers, and (3) implementation of narrow-line electric-quadrupole cooling and background-free imaging for ¹³³Cs. Together these results provide the experimental and theoretical foundation for assembling strongly interacting LiCs molecules suitable for neutral-atom quantum processors and simulation.
Upon joining the lab in 2021 I helped commission a dual-species chamber that already supported cesium tweezers but had yet to capture lithium, whose 3.5 µK photon-recoil energy and unresolved D-line hyperfine structure complicate laser cooling. We engineered a 671 nm Zeeman slower, nulled residual magnetic fields to the micro-tesla level, and optimized gray-molasses cooling in free space to overcome these challenges. By loading into a tweezer, the system produced the first single ⁶Li atom trapped in a 1064 nm tweezer and enabled 2000 consecutive images with a 99.95 % survival probability, establishing the benchmark for neutral-atom imaging fidelity at that time and supplying the lithium component required for LiCs molecule assembly. This helped bring Lithium into the mix for tweezer community around the world.
The unexpected efficiency observed with lithium exposed gaps in the trapped-atom cooling literature. We led the development of a master-equation model that treats motional and hyperfine dynamics on equal footing and integrates polarization-gradient, gray-molasses, Λ-enhanced, and Raman/Single-sideband schemes into a single analytic formalism. The resulting 20-page publication presents a cooling “phase diagram” that guides parameter selection across trap depths and species and is now widely used by groups pursuing motional ground-state preparation in optical tweezers. This has been especially useful for people starting out in the field as a quick review of the field.
We extended our neutral-atom platform by exploiting the narrow 6S₁∕₂ → 5D₅∕₂ electric-quadrupole transition in ¹³³Cs (λ = 685 nm, Γ/2π ≈ 117 kHz) to obtain background-free imaging and single-photon sideband cooling inside a 1064 nm optical tweezer. A Laguerre–Gaussian vortex beam delivered the excitation: its phase singularity was aligned with the trap centre so the atom experienced near-zero intensity, while cascade decay via 6P₃∕₂ produced 852 nm fluorescence that was readily isolated from the drive light. By encoding both orbital (ℓ = +1) and spin (σ = +1) angular momentum into the beam and adjusting the tweezer’s ellipticity to a magic value, we realised a closed |F = 4, mF = 4⟩ → |F′ = 6, m′F = 6⟩ cycle that delivered 99.58 % state-detection fidelity and cooled the atom to 5 µK in a 1.1 mK trap (⟨n_rad⟩ ≈ 0.8, ⟨n_ax⟩ ≈ 4.3). This is the first demonstration of quadrupole-based narrow-line cooling and background-free imaging for an alkali atom in a tweezer, and it adds a compact, single-beam technique that can improve gate fidelities in neutral-atom arrays, raise the efficiency of molecule assembly, and support miniature optical-clock architectures.
Lithium control, the unified cooling theory, and the cesium quadrupole toolbox jointly enable the next phase of the project: deterministic assembly of ground-state LiCs molecules whose permanent dipole moment is approximately 5.5 Debye, the largest among bi-alkali dimers. These strong, tunable dipole-dipole interactions are expected to support fast, high-fidelity two-qubit gates in scalable neutral-atom quantum-information architectures.