LL Lab

LL Lab explores how light and cold atoms interact, with a focus on quantum many-body physics. Our platform combines control over individual atoms with the collective coupling provided by an optical cavity. We use these capabilities to study quantum measurement and many-body entanglement, and to develop approaches to quantum computing and precision sensing.

We have integrated a controllable array of cold atoms with a high-performance optical cavity, achieving strong coupling between independently trapped atoms and a shared light field. Individual atoms can be positioned to form a chosen array, while the cavity allows them to interact with the same optical mode. We have characterized this coupling in both single-atom and multi-atom systems, bringing together the flexibility of atom arrays and the enhanced light–matter interaction of cavity quantum electrodynamics.

A central challenge is to achieve strong coupling while leaving enough room for an atom array and sufficient optical access to control it. An optical cavity confines light between two mirrors, allowing it to interact repeatedly with the atoms. Tighter confinement strengthens this interaction but can make the atoms harder to accommodate and manipulate. Through cavity development and integration with the atom-array apparatus, we have combined strong atom–photon coupling with the access needed to trap, observe, and position individual atoms.

Using this system, we have demonstrated fast, high-fidelity readout of a single atom's internal quantum state. Different atomic states affect the transmission of light through the cavity differently, allowing us to determine the state by detecting the transmitted light. This turns strong light–matter coupling into a practical measurement capability and provides a basis for measurement-based control and quantum information processing.

Building on these results, we aim to prepare and study entangled states of multiple atoms through cavity-mediated interactions. Entanglement creates correlations across a quantum system that can serve as a resource for computation and enhanced measurement. We are interested in combining collective evolution, individual-atom control, and optical measurement to generate states with different patterns of correlation. These include entangled spin states and resources for collective quantum operations. Our goal is to identify efficient ways to prepare these states, verify their entanglement, and put their correlations to use.

We also plan to combine cavity-assisted readout with feedback, using measurement outcomes to guide subsequent control and help prepare, correct, and stabilize quantum states. Measurement both reveals information and changes the state being measured; understanding and using this interplay is central to our approach. In precision sensing, we are interested in using many-atom entanglement to reduce measurement noise. By studying state preparation, readout, and sensing performance together, we aim to develop measurements with sensitivities beyond those attainable with independent atoms.