Yu Zhao-Xian

Quantum Statistical Behaviors of Interaction of an Atomic Bose–Einstein Condensate with Laser*

We have investigated quantum statistical behaviors of photons and atoms in interaction of an atomic Bose–Einstein condensate with quantized laser field. When the quantized laser field is initially prepared in a superposition state which exhibits holes in its photon-number distribution, while the atomic field is initially in a Fock state, it is found that there is energy exchange between photons and atoms. For the input and output states, the photons and atoms may exhibit the sub-Poissonian distribution. The input and output laser fields may exhibit quadrature squeezing, but for the atomic field, only the output state exhibits quadrature squeezing. It is shown that there exists the violation of the Cauchy–Schwartz inequality, which means that the correlation between photons and atoms is nonclassical.

The Atomic Tunneling Current in Two—Species Bose—Einstein Condensates

It is shown that the atomic tunneling current and the Shapiro-like steps strongly depend on the initial number of atoms in each condensate and the initial phase difference between the two condensates which are initially in even (odd) coherent states. The nonlinearity of interatomic interactions in the two condensates may lead to the atomic tunneling current and Shapiro-like step between the two condensates. It is found that the interatomic nonlinear interactions can induce the atomic tunneling current and Shapiro-like step between two condensates even though there does not exist the interspecies Josephson-like tunneling coupling. The static atomic tunneling current flows in positive or negative direction, which depends on the phase difference of the two-species condensates.

Tunneling Dynamics of the Halves of a Double-Well Trap Containing a Bose-Einstein Condensate

In this paper, we have studied tunneling dynamics of the halves of a double-well trap containing a Bose–Einstein condensate. It is found that there exist step structure and macroscopic quantum self-trapping of population difference of atoms, and exist Shapiro-like steps of atomic tunneling current. Both the population difference and the atomic tunneling current depend strongly on the total number of atoms and the initial phase difference.

Quantum Mechanical Effects in a Non-Dissipation Mesoscopic Coupled Circuit in the Presence of Source

Under the squeezed vacuum state, the quantum zero point fluctuations for both the charge and current of a non-dissipation mesoscopic coupled circuit in the presence of source are given. The quantum mechanical effects of this circuit at zero temperature are studied.

Self-Trapping State and Atomic Tunnelling Current of an Atomic Bose–Einstein Condensate Interacting with a Laser Field in a Double-Well Potential*

We present a theoretical treatment of dynamics of an atomic Bose–Einstein condensation interacting with a single-mode quantized travelling-wave laser field in a double-well potential. When the atom-field system is initially in a coherent state, expressions for the energy exchange between atoms and photons are derived. It is revealed that atoms in the two wells can be in a self-trapping state when the tunnelling frequency satisfies two specific conditions, in which the resonant and far off-resonant cases are included. It is found that there is an alternating current with two different sinusoidal oscillations between the two wells, but no dc characteristic of the atomic tunnelling current occurs. It should be emphasized that when without the laser field, both the population difference and the atomic tunnelling current are only a single oscillation. But they will respectively become a superposition of two oscillations with different oscillatory frequencies in the presence of the laser field. For the two oscillations of the population difference, one always has an increment in the oscillatory frequency, the other can have an increment or a decrease under different cases. These conclusions are also suitable to those of the atomic tunnelling current. As a possible application, by measurement of the atomic tunnelling current between the two wells, the number of Bose-condensed atoms can be evaluated. By properly selecting the laser field, the expected atomic tunnelling current can be obtained too.

q, s-Taylor's Formula with q, s-Remainder

The q, s-Taylors formula with its q, s-remainder by using the q, s-differentiation approach is given.

Amplitude Squeezing of a Weakly Interacting Bose System with Spontaneous U(1) Symmetry Breaking

We study the quantum fluctuations and the amplitude squeezing of a weakly interacting Bose system with spontaneous U(1) symmetry breaking. It is found that this system can exhibit amplitude squeezing.

Interaction of F =2 Spinor Bose Condensate with Driven External Magnetic Fields

We have studied the interaction of spinor Bose condensate with a combination of static and sinusoidal magnetic field . We find that the tunneling current among spin 0 and spin , spin 0 and spin , spin and spin may exhibit the incremental oscillation behavior, which depends on the field parameters of the reduced amplitudes of the transverse and the longitudinal magnetic fields respectively. This means that the dynamics spin localization can be adjusted experimentally by selecting the less values of the reduced amplitudes of the transverse magnetic field and those of the longitudinal magnetic field .

Atomic Tunneling Effect in Two-Component Bose-Einstein Condensates with a Coupling Drive*

In this paper, we have studied the atomic population difference and the atomic tunneling current of two-component Bose-Einstein condensates with a coupling drive. It is found that when the two-component Bose-Einstein condensates are initially in the coherent states, the atomic population difference may exhibit the step structure, in which the numbers of the step increase with the decrease of the Rabi frequency and with the increment of the initial phase difference. The atomic population difference may exhibit collapses, and revivals, in which their periods are affected dramatically by the Rabi frequency and the initial phase difference. The atomic tunneling current may exhibit damping oscillation behaviors, and exist the step structure for the time range of second.

Tunneling Dynamics of Two-Species Bose–Einstein Condensates

We have studied the tunneling dynamics of two-species Bose–Einstein condensates. It is shown that the population difference and the Josephson-like tunneling current between the two condensates exhibit oscillation behaviors and there exists macroscopic quantum self-trapping, which strongly depends on the initial state, interatomic nonlinear self-interaction, interspecies nonlinear interaction, and the total number of atoms in the two condensates.