Linear optics substituting scheme for multi-mode operations

We propose a scheme allowing a conditional implementation of suitably truncated general single- or multi-mode operators acting on states of traveling optical signal modes. The scheme solely relies on single-photon and coherent states and applies beam splitters and zero- and single-photon detections. The signal flow of the setup resembles that of a multi-mode quantum teleportation scheme thus allowing the individual signal modes to be spatially separated from each other. Some examples such as the realization of cross-Kerr nonlinearities, multi-mode mirrors, and the preparation of multi-photon entangled states are considered.Comment: 11 pages, 4 eps-figures, using revtex

Effective Hamiltonian Theory and Its Applications in Quantum Information

This paper presents a useful compact formula for deriving an effective Hamiltonian describing the time-averaged dynamics of detuned quantum systems. The formalism also works for ensemble-averaged dynamics of stochastic systems. To illustrate the technique we give examples involving Raman processes, Bloch-Siegert shifts and Quantum Logic Gates.Comment: 5 pages, 3 figures, to be published in Canadian Journal of Physic

Producing the event ready two photon polarization EPR state with linear optics devices

We propose a scheme to produce the maximally two photon polarization entangled state(EPR state) with single photon sources and the linear optics devices. In particular, our scheme requires the photon detectors only to distinguish the vacuum and non-vacuum Fock number states. A sophisticated photon detector distinguishing one or two photon states is unnecessary.Comment: Published in Phys. Rev. A alread

Efficient scheme for one-way quantum computing in thermal cavities

We propose a practical scheme for one-way quantum computing based on efficient generation of 2D cluster state in thermal cavities. We achieve a controlled-phase gate that is neither sensitive to cavity decay nor to thermal field by adding a strong classical field to the two-level atoms. We show that a 2D cluster state can be generated directly by making every two atoms collide in an array of cavities, with numerically calculated parameters and appropriate operation sequence that can be easily achieved in practical Cavity QED experiments. Based on a generated cluster state in Box$^{(4)}$ configuration, we then implement Grover's search algorithm for four database elements in a very simple way as an example of one-way quantum computing.Comment: 6 pages, 3 figure

Generation of arbitrary two dimensional motional state of a trapped ion

We present a scheme to generate an arbitrary two-dimensional quantum state of motion of a trapped ion. This proposal is based on a sequence of laser pulses, which are tuned appropriately to control transitions on the sidebands of two modes of vibration. Not more than $(M+1)(N+1)$ laser pulses are needed to generate a pure state with upper phonon number $M$ and $N$ in the $x$ and $y$ direction respectively.Comment: to appear in PR

Conditional generation of arbitrary multimode entangled states of light with linear optics

We propose a universal scheme for the probabilistic generation of an arbitrary multimode entangled state of light with finite expansion in Fock basis. The suggested setup involves passive linear optics, single photon sources, strong coherent laser beams, and photodetectors with single-photon resolution. The efficiency of this setup may be greatly enhanced if, in addition, a quantum memory is available.Comment: 7 pages, 5 figure

Study of J/ψ→ωK+K−J/\psi \to \omega K^+K^-

New data are presented on $J/\psi \to \omega K^+K^-$ from a sample of 58M $J/\psi$ events in the upgraded BES II detector at the BEPC. There is a conspicuous signal for $f_0(1710) \to K^+K^-$ and a peak at higher mass which may be fitted with $f_2(2150) \to K\bar K$. From a combined analysis with $\omega \pi ^+ \pi ^-$ data, the branching ratio $BR(f_0(1710)\to\pi\pi)/BR(f_0(1710) \to K\bar K)$ is $< 0.11$ at the 95% confidence level.Comment: 11 pages, 5 figures. Submitted to Phys. Lett.

Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure

Study of J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar

The branching ratios and Angular distributions for J/psi decays to Lambda Lambdabar and Sigma0 Sigma0bar are measured using BESII 58 million J/psi.Comment: 11 pages, 5 figure

The σ\sigma pole in J/ψ→ωπ+π−J/\psi \to \omega \pi^+ \pi^-

Using a sample of 58 million $J/\psi$ events recorded in the BESII detector, the decay $J/\psi \to \omega \pi^+ \pi^-$ is studied. There are conspicuous $\omega f_2(1270)$ and $b_1(1235)\pi$ signals. At low $\pi \pi$ mass, a large broad peak due to the $\sigma$ is observed, and its pole position is determined to be $(541 \pm 39)$ - $i$ $(252 \pm 42)$ MeV from the mean of six analyses. The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL