Collectively induced transparency and absorption in waveguide quantum electrodynamics with Bragg atom arrays

Collective quantum states, such as subradiant and superradiant states, are useful for controlling optical responses in many-body quantum systems. In this work, we study novel collective quantum phenomena in waveguide-coupled Bragg atom arrays with inhomogeneous frequencies.For atoms without free-space dissipation, collectively induced transparency is produced by destructive quantum interference between subradiant and superradiant states. In a large Bragg atom array, multi-frequency photon transparency can be obtained by considering atoms with different frequencies. Interestingly, we find collectively induced absorption(CIA) by studying the influence of free-space dissipation on photon transport. Tunable atomic frequencies nontrivially modify decay rates of subradiant states. When the decay rate of a subradiant state equals to the free-space dissipation, photon absorption can reach a limit at a certain frequency. In other words, photon absorption is enhanced with low free-space dissipation, distinct from previous photon detection schemes. We also show multi-frequency CIA by properly adjusting atomic frequencies. Our work presents a way to manipulate collective quantum states and exotic optical properties in waveguide quantum electrodynamics(QED) systems.

A universal algorithm for defect-free atomic array with arbitrary periodic geometries[Invited]

The defect-free neutral atom array has emerged as an ideal platform to investigate complex many-body physics of interacting quantum particles,offering the opportunities for quantum simulation and quantum-enhanced metrology.To fast build a large-scale quantum system,we design a sorting-atom algorithm with maximum parallelisms.Compared with previous protocols,our method saves the rearrangement time by sorting row-by-row and is also universal to arbitrary periodic patterns with no need to change the hardware.We present the generation of a defect-free square and other periodic geometries and demonstrate the potential to scale up a defect-free array to 2500 atoms with only about 180 steps of rearrangement.

Magnetic focusing of cold atomic beam with a 2D array of current-carrying wires

A new scheme to realize a two-dimensional （2D） array of magnetic micro-lenses for a cold atomic beam. formed by an array of square current-carrying wires, is proposed. We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms, and study the dynamic focusing processes of cold atoms passing through the mag- netic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method. The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam, even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.