Zhou Shu-Yu

Narrowband Biphoton Generation with Four-Wave Mixing in a Far-Detuning Three-Level System

Non-classical paired photons are generated by a four-wave mixing process in a far-detuning three-level system with cold atoms. A violation of the Cauchy-Schwartz inequality of a factor of 310 is observed. This phenomenon shows that paired photons have a non-classical correlation. The experimental results are compared with theoretical results obtained using perturbation theory. The oscillation frequencies of the two-photon intensity correlation functions are in reasonable agreement with the effective Rabi frequencies of the coupling laser. However, we find that the dephasing rates (or decay rates) observed are far larger than the theoretical values.

Evidence for a Bose-Einstein Condensate in Dilute Rb Gas by Absorption Image in a Quadrupole and Ioffe Configuration Trap

We report the realization of Bose-Einstein condensation (BEC) in dilute rubidium gas. The BEC was achieved in a quadrupole and Ioffe configuration trap. The number of condensed atoms is around 4×104 in total 5×105, and the transition temperature is 250 nK. We have studied the light scattering of the atom cloud and the condensate in a tightly confined magnetic trap. We show that it is possible to use the diffraction patterns in the near-resonant imaging of the trapped cold atomic samples to give the information of the BEC phase transition.

Production and measurement of Bose-Einstein condensate of ~(87)Rb atomic gas

The research platform for Bose-Einstein condensate in 87Rb atomic gas, which is composed of a double MOT configuration and a QUIC trap, was reported. The properties of the condensate were measured both in time-of-flight and in tight confinement by the absorption imaging method. The measurements agreed with the criterions of Bose-Einstein condensation phase transition. About 2×105 atoms were pure condensed.

Trapping of neutral Rb-87 atoms on an atomchip

We report an experiment of trapping of neutral Rb-87 atoms on a, self-made atomchip. The H-shaped atomchip is made by magnetron sputtering technology, which is different from the atomchip technology of other teams. We collect 3 x 10(6) Rb-87 atoms in the mirror magneto-optical trap (MOT) using the external MOT coils, and 1 X 10(5) Rb-87 atoms are transferred to U-MOT using U-shaped wire in chip and a pair of bias coils.

Radio-Frequency Field-Induced Quantum Interference Effects in Cold Atoms

We propose constructing a quantum interference configuration for cold atoms in a magneto-optical trap by applying a radio frequency field, which coherently couples adjacent Zeeman sublevels, in combination with a repumping laser field. One effect of this interference is that a dip exists in the absorption of the repumping light when the radio frequency is scanned. Our prediction has been indirectly detected through the fluorescence of cold atoms in a preliminary experiment.

Single-Qubit Operations for Singlet-Triplet Qubits in an Isolated Double-Well with Fixed Tunneling

We propose a scheme to implement single-qubit operations for singlet-triplet qubits located in an isolated double-well potential with fixed inter-site tunneling when superexchange interactions predominate. Arbitrary single-qubit gates can be realized by a sequence composed of two elementary operations which can be switched between different parameter regimes by adjusting slightly the relative energy bias of trapped atoms in each sub-well site. The experimental feasibility of the strategy and the fidelity of basic rotation operations are also analyzed.

Experimental Properties of Optical Phase Conjugation in Cold Atoms in a Magneto-Optical Trap

We employ a sample of cold 87Rb atoms in a magneto-optical trap to study the impulse responses and spatial characters of backward conjugate waves in a four-wave mixing process. We measure the slow and superluminal group velocities of backward conjugate waves, and find the sensitive variation of the spatial mode of backward waves with the probe-pump detuning and the dependence of the reflectance on the magnetic field, while the trapping magnetic field exists.

Effects of Atom-Atom Interaction on Localization and Adiabaticity of BEC in One-Dimensional Disorder Optical Lattice

We numerically simulate the dynamical behavior of BEC in one-dimensional incommensurable optical lattice by split-step Fourier method in a time-dependent one-dimensional Gross—Pitaevskii equation. It is indicated that the atom-atom interaction will weaken the localization and broaden the wave function, and it will destroy the adiabaticity of the ramped loading process in both single lattice and incommensurate lattice due to the broadening effect. A band structure model can interpret the difference of the adiabatic condition with non-interacting BEC in these optical lattices.

Abnormal Phenomenon of ac Stark splitting in Magneto-Optical Traps

We experimentally study the ac Stark splitting in D2 line of cold 87Rb atoms. The frequency span between the Autler–Townes doublets is obviously larger than that derived from theoretical calculation. Two physical effects, which increase the effective Rabi frequency, contribute to the splitting broadening. First, atoms tend to distribute in strong field places of a inhomogeneous red-detuned light field. Second, atoms reabsorb scattered light when they are huge in number and high in density.

Continuous Imaging of a Single Neutral Atom in a Variant Magneto-Optical Trap

We demonstrate continuous imaging of a single 87Rb atom confined in a steep magneto-optical trap with an electron-multiplying charge-coupled device (EMCCD) camera and realize a one-dimensional micro-optical trap array with a Dammann grating. We adopt several methods to reduce the noise in the fluorescence signal we obtain with the EMCCD. Step jumping characteristics of the fluorescence demonstrate capturing and losing of individual atoms.