quantum computing

Neutral atom-based single atom arrays offer several advantages for quantum computing, including scalability, high fidelity control, and coherent transport. Leveraging these benefits, we selected Cesium atoms to create a magneto-optical trap and utilized optical tweezers to capture the ten-by-ten single atoms array. In our basic single-atom characterization measurements, we achieve an average loading rate of approximately 60%, an atom lifetime of 3.68 seconds, and a temperature of 15.02μK. The Rabi oscillation is first damonstrated through microwave, giving a Rabi frequency of 17kHz.

3D MOT fluorescence imaging and optical tweezer array generation

We aim to implement a high-fidelity single-qubit gate on Cesium atoms via a two-photon Raman transition. To generate the required light fields, a D1-line laser is phase-modulated and subsequently converted to amplitude-modulated sidebands via reflection from a dispersive chirped Bragg grating (CBG). Preliminary measurements show that the strength of the amplitude-modulated sidebands depends on the phase-modulation depth, in agreement with the expected Bessel-function dependence. Ongoing work includes measuring Rabi oscillations between hyperfine ground states and determining the coherence time T₂* of the qubit, which will complete the evaluation of the single-qubit gate performance.                                                              Physical Review A 105.3 (2022): 032618

To achieve high-fidelity two-qubit Rydberg gates, we constructed a dual-wavelength external-cavity diode laser (ECDL) system at 1039 nm and 918 nm, both stabilized to an ultra-low expansion (ULE) cavity using the Pound–Drever–Hall technique. The 918 nm laser is frequency-doubled to 459 nm. We use 459nm and 1039nm laser to excite cesium atoms to Rydberg states. The system achieves a frequency noise of 350 Hz and a long-term drift of 7 kHz per day, providing the narrow linewidth and phase stability required for coherent two-qubit Rydberg gate operations.

We shape Gaussian beams into flat-top profiles using phase-only SLMs to obtain uniform Rabi frequencies for parallel two-qubit Rydberg gates. Starting from analytic phase functions or a modified Gerchberg–Saxton algorithm, we iteratively optimize Zernike polynomials (with simulated annealing) to suppress optical aberrations while retaining high diffraction efficiency. We further characterize intrinsic SLM imperfections—Fabry–Pérot cavity effects, inter-pixel crosstalk, and backplane phase/offset—and include them in a physics-based forward model to guide optimization. Experimentally, we achieve <1.3% flat-top roughness and ~92% effective diffraction efficiency, delivering highly uniform, power-efficient addressing beams.

Measured flat-top beam profiles for (a) rectangular, (b) square, and (c) circular target shapes, shown with horizontal/vertical cross-sections and corresponding RMS uniformity values. The rectangular beam exhibits smooth Fourier-limited edges (RMS_all=5.59%, RMS_2D=1.14%). The square flat-top shows a constant plateau with sharp boundaries (RMS_all​=8.57%, RMS_2D​=1.95%). The circular beam presents a smooth radial profile (RMS_all=8.20%, RMS_2D​=1.84%). 

We investigate background-free state detection in cesium atoms using the narrow 6S₁/₂ → 5D₅/₂ electric quadrupole transition at 685 nm. By constructing an iodine saturated absorption spectrum, we stabilize the laser frequency and resolve its hyperfine structure at 14596.7025 cm⁻¹. This scheme enables high-fidelity fluorescence detection with minimal background noise and paves the way for narrow-line cooling, single-atom imaging, and future high-finesse cavity locking for improved coherence in Rydberg-based quantum gates.

Defect-free atom arrays are a crucial prerequisite for realizing scalable neutralatom quantum computation and simulation. To achieve such arrays, we develop a PC-based feedback control system that performs realtime calculation of rearrangement sequences and commands a fieldprogrammable gate array (FPGA) to generate the desired multifrequency radio-frequency (RF) signals. These signals drive an acoustooptic deflector (AOD) to assemble onedimensional or two-dimensional defect-free atom arrays. We simulate the full pipeline by generating random atomloading matrices and capture the rearrangement process using a CCD camera. The system is fully compatible with loaded singleatom arrays and can be applied to future rearrangement experiments.