Yan Lab - Research

The ability to precisely control and program quantum systems is transforming the way we tackle problems in physical science and computation. Among the various quantum platforms, optically trapped neutral atoms stand out for their exceptional scalability and ease of reprogramming and reconfiguration. However, implementing fault-tolerant quantum operations on atomic systems remains highly resource-intensive, often requiring multiple rounds of quantum gates and partial measurements.

At the Yan Lab, we aim to develop neutral atom quantum systems with scalable long-range interactions, and designed to be compatible with non-destructive readout and feedback-based error correction. The systems we develop will be well-suited for quantum simulations and algorithms that are robust against noise and errors from various sources.

Strontium Arrays in an Optical Cavity

Long-range quantum gates and cavity selective-radiance

Photon exchange between atomic qubits in a high-finesse optical cavity enables effectively infinite-range interactions and any-to-any connectivity, providing a powerful resource for implementing error-correction codes and multi-qubit gates. At visible and near-infrared wavelengths, however, the fidelity of cavity-mediated interactions is limited by photon losses. In strontium, the mid-infrared transition at 2.9 µm between the metastable spin-triplet 5P and 4D states offers a pathway to much coherent atom–light coupling. The atom-photon interaction strength scales with the square of the wavelength, while mirror scattering losses decrease inversely with the square of the wavelength. As a result, cavity quantum electrodynamics (QED) at long wavelengths supports far more robust quantum interactions between atoms.

Operating cavity QED at mid-infrared wavelengths also allows the atoms to be arranged in a sub-wavelength array using visible wavelength optical tweezers. In this regime, the collective emission rate into the cavity—which mediates interactions—and into free space—which causes decoherence—can be independently controlled. This makes it possible to engineer selective-radiance configurations, where photon loss to free space is suppressed through destructive interference while coupling to the cavity is superradiantly enhanced. Such control establishes a new experimental paradigm for mitigating quantum decoherence.

Lithium Gases and Qubits

Controling many-body systems and quantum circuits through measurement and feedback

Analog quantum simulators based on ultracold neutral atoms have been highly successful in simulating strongly correlated many-body quantum systems, including mapping phase diagrams and quantitatively measuring thermodynamic and transport properties. To access certain elusive phases—such as the long-sought superfluid state in Fermi–Hubbard systems—these platforms must reach even lower entropy states.

Our group is developing measurement-based feedback techniques to reduce entropy and gain greater control over many-body quantum systems. We use ultracold lithium gases—atoms with fermionic quantum statistics and tunable interactions—coupled to a high-finesse optical cavity. Light transmitted through the cavity provides a non-destructive readout of density and spin dynamics, which can then be fed back to steer the system into desired quantum states.

In addition, lithium’s unique properties—low atomic mass, rapid movement, and good cycling transitions—make it an excellent platform for implementing quantum error correction codes. We plan to explore its potential as digital qubits, with Rydberg excitations to induce controlled interactions between individually tweezed lithium atoms.

Atomic Physics on the Cloud

In recent years, the advent of commercially available quantum computers has enabled the scientific community to explore both near-term quantum applications and the fundamental physics of qubits through remote experimental platforms. Our interests include investigating collective effects in the decay and decoherence of Rydberg atom arrays, such as superradiant photon emission or interactions with spontaneously generated contaminant states. We are also exploring the implementation of fault-tolerant quantum algorithms on alkali-metal and alkaline-earth neutral atom systems available via various cloud platforms.

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