Implementation Of A Magic-wavelength Optical Tweezer For Cesium Atoms And Improvement Of Single Atom's Trapping Lifetime

As the most basic quantum bit,single atom plays a unique role in the study of the basic principle of the interaction between light and matter,and can provide a powerful tool for the construction of quantum computing,quantum communication and multi-quantum node network.Compared with other quantum systems,neutral atoms have the advantages of easy manipulation,small interaction with the external electromagnetic field and longer coherence time.Based on the basic theory of interaction between light and a two-level atom,by using the multilevel model to calculate the cesium atoms in optical dipole trap the light shift,and then construct the magic wavelengths trap,due to the atom's lifetime in magic wavelengths is very short,We use the harmonic oscillator model to analyze the heating mechanism of atoms in the dipole trap,then added a set of power stability of feedback systems,partly reduce the intensity noise of dipole trap,and the heating parameters of atoms in the dipole trap,thus improve the life of single atom trapping.This paper mainly includes the following parts:?1?Introduce the basic theory of the interaction between monochromatic light and two-level atom,as well as the laser cooling and trapping of single atom and the construction of single-atom array.Single atom and single atom array as the most basic quantum bits in quantum computing,quantum information applications.?2?Introduce the atomic energy level frequency shift caused by the optical dipole well,and use the multi-level model to calculate the optical frequency shift of cesium atom D2 line 6S_1/2 F=4,m_F=+4 6P_3/2 F^'=5,m_F=+5 under different wavelength and polarization dipole trap.The wavelength with zero difference frequency shift between ground state and excited state is determined?we call it magic number wavelength?,then the optical dipole trap of magic number wavelength is constructed,and the optical frequency shift of single atom in magic number wavelength optical dipole trap is measured.As a good single photon source,single atom can effectively compress the line width of atomic radiated photons,which is close to the natural line width,by selecting magic number wavelength to make the differential light shift of upper and lower energy levels zero,which is of great practical significance for improving the quality of single photon source.?3?A power stability feedback system is added to solve the problem that the intensity fluctuation of the optical dipole trap heats the atoms in the trap.AOM is used as the main control element,sampling part of the output power,as the feedback signal input PID,PID output as the modulation signal,feedback in AOM driving voltage,AOM can stabilize the output of first-order diffraction light,and reduce part of frequency domain noise,as well as time domain noise.?4?Reducing the dipole trap intensity noise can effectively prolong the life of atoms in the dipole trap.We compare the power stability feedback effect in time domain with different sampling power proportion and the bandwidth suppression effect in frequency domain with the same sampling power proportion.Then,the capture lifetime of the atoms in the dipole trap was measured under the power feedback system on or off.The experiment results showed that the atomic capture lifetime could be extended from 200 ms to 1180 ms by suppressing the photoactive noise of the dual dipole well.