Measurement And 3D Reconstruction Of The Micro-scale Blue Detuned Trap For Single Atom Manipulation

Due to the rapidly development of quantum physics, quantum coherent manipulation system has attracted much attention. Single quantum dots, single electron, superconducting loop, single trapped atom and single trapped ion are the most common quantum systems. Compared to other systems, single isolated atom with long coherent time is a relatively "clean" quantum system. Manipulation of single atoms plays a key role in studying quantum behavior of single particles. As a powerful tool to achieve neutral single atomic trapping, constructing and measuring a micro-scale optical dipole trap (ODT) is the base for single atomic control.ODT is used for single atomic trap based on the gradient field induced force which is formed by a focused light field. Usually there are two kinds of ODTs for trapping single atom:the red detuned trap and the blue detuned trap. Because of its simple structure, the red detuned trap becomes a more commonly used ODT. In principle, in the red detuned trap, the atoms are trapped at the maximum intensity position due to the dipole force, the coherence destruction and the heating effect from the laser is relatively obvious. But in the blue detuned trap, atomic dipole force directed to the weakest intensity areas and the influence from photons is greatly reduced. So, the blue detuned trap is more conducive to accurately study the quantum behavior of single atoms. However, the structure of micro-scale blue detuned trap is more complex than the red detuned trap and it is more difficult to construct and measure a blue micro-trap. Meanwhile, due to the presence of "collisional blockade" effect, in order to achieve the trapping of single atoms, the typically size of the optical dipole trap is on the micrometer scale and the precision measurement is a challenge. In order to eliminate the effect of the photons to the trapping atoms and to get single atoms with good coherence, we construct the micro-scale blue detuned dipole trap and experimentally study its structure and the ability to capture a single atom. In the experiment, we get the micro-scale ODT by crossing two focused Laguerre-Gaussian beams whose waist is 1.5μm at the position of the intersection of the waist. We then obtain the CCD image in the x-y plane, which is amplified by a special set of lens, and reconstruct the trap structure in x-z and y-z planes, and thereby reconstruct a three-dimensional structure of the ODT. In addition, we estimate some parameters in the dipole trap for cesium atoms. This work has significance for us to achieve the single atomic manipulation in the blue detuned trap.