Research

Cooling, imaging, and assembling quantum matter one atom at a time.

The lithium-cesium program in the Hood Lab has progressed through three linked milestones: single-atom lithium trapping and high-fidelity imaging, a unified theory of optical cooling for trapped atoms with spin, and narrow-line electric-quadrupole cooling and background-free imaging of cesium.

Lithium

experiment

From MOT to record-survival imaging

Upon joining the lab in 2021, I helped commission a dual-species chamber that already supported cesium tweezers but had not yet captured lithium. Lithium's 3.5 microkelvin photon-recoil energy and unresolved D-line hyperfine structure make cooling and imaging unusually demanding.

We engineered and optimized the lithium apparatus, including 671 nm slowing/cooling light, magnetic-field control, gray-molasses cooling, tweezer loading, and D1 Λ-enhanced gray-molasses imaging. The system produced single 6Li atoms in a 1064 nm tweezer and enabled 2000 consecutive images with 99.950% per-image survival.

Theory

master equation

One framework for sub-Doppler cooling in tweezers

The unexpected efficiency of lithium Λ-GM imaging exposed gaps in the trapped-atom cooling literature. We developed a master-equation model that treats motional and hyperfine dynamics on equal footing, unifying polarization-gradient cooling, gray molasses, Λ-enhanced gray molasses, EIT-like cooling, and Raman/sideband schemes.

The resulting work gives a common language for designing cooling protocols across atom species and trap depths, and it now serves as a compact theoretical reference for groups pursuing motional ground-state preparation in optical tweezers.

Cesium

narrow-line

Quadrupole cooling and background-free imaging

We extended the neutral-atom platform by exploiting the narrow 6S1/2 → 5D5/2 electric-quadrupole transition in 133Cs at 685 nm. A Laguerre-Gaussian vortex beam drives the excitation while cascade decay through 6P3/2 produces 852 nm fluorescence that is easily separated from the drive light.

By combining orbital and spin angular momentum in the beam and tuning the tweezer ellipticity to a magic value, we realized a closed stretched-state cycle with 99.58% state-detection fidelity and cooled the atom to about 5 microkelvin in a 1.1 mK trap.

LiCs molecules

Toward dipolar LiCs processors

Lithium control, cooling theory, and the cesium quadrupole toolbox jointly enable the next phase: deterministic assembly of ground-state LiCs molecules. LiCs has a permanent dipole moment of roughly 5.5 Debye, making it a strong candidate for dipolar quantum simulation and molecule-based quantum information.

The immediate technical path runs through dual-species trapping, Feshbach spectroscopy, sympathetic cooling, motional ground-state preparation, magnetoassociation, and optical transfer to the rovibrational ground state.

Tools I use

Experimental and theoretical toolkit

Optics

Optical tweezers
AOM beam control
High-NA imaging
Structured light

Atoms

6Li and 133Cs
MOTs and molasses
Optical pumping
State-resolved detection

Theory

Lindblad master equations
Lamb-Dicke physics
Cooling rate models
QuTiP simulations

Direction

LiCs molecules
Neutral-atom QC
Dipolar simulation
Precision spectroscopy