We investigate the different characteristics of the intensity noise of a laser-diode-pumped single-frequency Vring Nd: YVO4 laser and a Nd: YVO4 KTP green laser. By use of an optoelectronic feedback circuit connected directly to the pump current of the laser diode, the low-frequency intensity noise of the intracavity frequency doubler was suppressed to some extent.

We propose a scheme for transferring quantum states from the propagating light fields to macroscopic, collective vibrational degree of freedom of a massive mirror by exploiting radiation pressure effects. This scheme may prepare an Einstein-Podolsky-Rosen state in position and momentum of a pair of distantly separated movable mirrors by utilizing the entangled light fields produced from a nondegenerate optical parametric amplifier.

We propose a scheme for producing entangled spin-squeezed states of an atomic ensemble inside an optical cavity by backaction of a detuned quantum-nondemolition (QND) measurement. By illuminating the atoms with bichromatic light, an interaction Hamiltonian of the cross-Kerr effect between the cavity and atoms is generated to implement QND measurements. The feedback effect is obtained through mixing the phase and amplitude quadratures of the cavity field, due to the detuning of the optical cavity. Therefore the continuous nondemolition measurements are fed back to correct the quantum state of the atomic sample such that unconditional spin squeezing is produced without requiring the use of any external electronics.

A tripartite entangled state of bright optical field is experimentally produced using an Einstein- Podolsky-Rosen entangled state for continuous variables and linear optics. The controlled dense coding among a sender, a receiver, and a controller is demonstrated by exploiting the tripartite entanglement. The obtained three-mode "position" correlation and relative "momentum" correlation between the sender and the receiver, and thus the improvements of the measured signal to noise ratios of amplitude and phase signals with respect to the shot noise limit are 3.28 and 3.18 dB, respectively. If the mean photon number n equals 11 the channel capacity can be controllably inverted between 2.91 and 3.14. When n is larger than 1.0 and 10.52, the channel capacity of the controlled dense coding is predicted to exceed the ideal single channel capacity of coherent and squeezed state light communication, respectively.

Simple schemes to realize quantum teleportation and dense coding for continuous variables are proposed, in that entangled EPR beams are produced by combining two bright amplitude squeezed beams. The measurement of the "Bell state" is accomplished by means of direct detection for photocurrents and two rf power splitters. As a local oscillator and balanced homodyne detector are not needed, the proposed system is easy to realize experimentally.

We report Bose-Einstein condensation of weakly bound 6Li2 molecules in a crossed optical trap near a Feshbach resonance. We measure a molecule-molecule scattering length of 170+100-60nm at 770G, in good agreement with theory. We study the 2D expansion of the cloud and show deviation from hydrodynamic behavior in the BEC-BCS crossover region.

We report the observation of three p-wave Feshbach resonances of 6Li atoms in the lowest hyperfine state f=1/2. The positions of the resonances are in good agreement with theory. We study the lifetime of the cloud in the vicinity of the Feshbach resonances and show that, depending on the spin states, two-or three-body mechanisms are at play. In the case of dipolar losses, we observe a nontrivial temperature dependence that is well explained by a simple model.

Highly efficient quantum dense coding for continuous variables has been experimentally accomplished by means of exploiting a bright Einstein-Podolsky-Rosen (EPR) beam with anticorrelation of amplitude quadratures and correlation of phase quadratures. Two bits of classical information are encoded on two quadratures of a half of a bright EPR beam, then are simultaneously decoded by the other half of the EPR beam with the sensitivities beyond that of the shot noise limit. A high degree of immunity to unauthorized eavesdropping has been experimentally demonstrated.

In this paper we present a scheme in which the amplitude-quadrature difference and phase-quadrature difference of two bright nonclassical beams serve as a pair of observed complementary variables that can be measured directly and can form a new squeezed state. Mixing such two quadrature-difference squeezed-state beams on a beam splitter produces characteristic of the Einstein-Podolsky-Rosen quantum entanglement. The experimental schemes producing such nonclassical beams and its possible applications in quantum information are discussed.

In this paper we investigate the squeezing of a finite-bandwidth optical field which may be thought of as originating from Einstein-Podolsky-Rosen-(EPR-) like quantum correlations between the upper and lower sidebands. Ordinarily, when EPR pairs are created from such a resource, the bandwidth is preserved, and the signal-to-noise ratio of the quadrature correlations is reduced. Here we show that by using frequencydependent beam splitters we may create N EPR pairs from a single finite-bandwidth squeezed beam with no reduction in the correlations's signal-to-noise ratio. However, the bandwidth is reduced by a factor of N relative to the original squeezed beam. Because this transformation is linear it may be inverted to retrieve the single squeezed beam from the corresponding N EPR pairs.