Comparison of two absorption imaging methods to detect cold atoms in magnetic trap

Two methods of absorption imaging to detect cold atoms in a magnetic trap are implemented for a high-precision cold atom interferometer.In the first method,a probe laser which is in resonance with a cycle transition frequency is used to evaluate the quantity and distribution of the atom sample.In the second method,the probe laser is tuned to an open transition frequency,which stimulates a few and constant number of photons per atom.This method has a shorter interaction time and results in absorption images which are not affected by the magnetic field and the light field.We make a comparison of performance between these two imaging methods in the sense of parameters such as pulse duration,light intensity,and magnetic field strength.The experimental results show that the second method is more reliable when detecting the quantity and density profiles of the atoms.These results fit well to the theoretical analysis.

Production of Rubidium Bose-Einstein Condensate in an Optically Plugged Magnetic Quadrupole Trap

We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.

High-Performance Sodium Bose-Einstein Condensate Apparatus with a Hybrid Trap and Long-Distance Magnetic Transfer

We report on the production of large sodium Bose^Einstein condensates in a hybrid of magnetic quadrupole and optical dipole trap. With an optimized spin-flip Zeeman slower, 2 ~ 1010 sodium atoms are captured in the magneto-optical trap （MOT）. A long distance magnetic transfer setup moves the cold atom over 46cm from the MOT chamber to the UHV science chamber, which provides great optical access and long conservative trap lifetime. After evaporative cooling in the hybrid trap, we produce nearly pure condensates of 1 ~ 107 atoms with lifetime of 80 s in the optical dipole trap.

Photostop of iodine atoms from electrically oriented ICl molecules

The dynamics of photostopping iodine atoms from electrically oriented ICI molecules was numerically studied based on their orientational probability distribution functions. Velocity distributions of the iodine atoms and their production rates were investigated for orienting electrical fields of various intensities. For the IC1 precursor beams with an initial rotational temperature of ~ 1 K, the production of the iodine atoms near zero speed will be improved by about ~ 5 times when an orienting electrical field of ~ 200 kV/cm is present. A production rate of ~ 0.5%0 is obtained for photostopped iodine atoms with speeds less than 10 m/s, which are suitable for magnetic trapping. The electrical orientation of IC1 precursors and magnetic trapping of photostopped iodine atoms in situ can be conveniently realized with a pair of charged ring magnets. With the maximal value of the trapping field being ~ 0.28 T, the largest trapping speed is ~ 7.0 m/s for the iodine atom.

Laser-manipulated the of a harmonically multiphoton transitions trapped particle

A single particle magneto-confined in a one-dimensional （1D） quantum wire experiences a harmonic potential, and imposing a sharply focused laser beam on an appropriate site shapes a δ potential. The theoretical investigation has demonstrated that for a sufficiently strong δ pulse the quantum motional stationary state of the particle is one of the eigenstates of the free harmonic oscillator, and it is determined by the site of the laser beam uniquely, namely a quantum state is admissible if and only if the laser site is one of its nodes. The numerical computation shows that all the nodes of the lower energy states with quantum numbers n ≤ 20, except the coordinate origin, are mutually different. So we can manipulate the multiphoton transitions between the quantum states by adjusting the position of the laser δ pulse and realize the transition from an unknown higher excitation state to a required lower energy state.

Stokes Representation for the Solutions of Maxwell-Vlasov

Maxwell-Vlasov PDEs system describes the dynamics of plasma consisting of charged particles with long-range inter-action. Their solutions can be written using some Stokes potentials. Section 1 presents the experimental devices which can produce a magnetic trap. Magnetic geometric dynamic provides mathematical tools for describing the magnetic flow (see [1-7]). Stokes representation for the solutions of PDEs as Maxwell PDEs or Maxwell-Vlasov PDEs are used analyzing electromagnetic energy in magnetic traps. Section 2 studies Maxwell-Vlasov PDEs system. Stokes represen-tation of its solutions, using Maximum Principle for a multitime optimal control problem, is obtained. Section 3 dis-cusses a method for changing a given ODEs system into a geodesic motion under a gyroscopic field of forces (geomet-ric dynamics). Section 4 proposes a modified form for Maxwell-Vlasov PDEs, by replacing the classical gyroscopic force with the one appearing in geometric dynamics. Stokes representation for the solutions of modified Max-well-Vlasov PDEs is also obtained.

AC magnetic trap for cold paramagnetic molecules

Strong-field-seeking states are the lowest-energy configurations for paramagnetic molecules in the magnetic field.Molecules in strong-field-seeking states cannot be trapped in a magnetostatic field because a magnetostatic maximum in free space is not allowed.In this paper,we propose an AC magnetic trap composed of two pairs of Helmholtz coils.The spatial magnetic field distribution is numerically calculated and the time-sequential control is depicted.We investigate the influence of the switching frequency and the electric current in the coils on the performance of our trap.Variations of the location and phase-space distribution during a whole switching cycle are simulated.Finally,we study the impact of time during which the field is switched off on the number of captured molecules in a switching cycle.