S-D Mixing and Searching for the psi(1P1) State at the Beijing Electron-Positron Coolider

The psi(1P1) state can be produced at the Beijing Electron-Positron Collider (BEPC) in the process psi'-->psi(1P1)+pi(0). We calculate the rate of this process taking account of the S-D mixing effect in psi'. It is shown that the rate is about a factor of 3 smaller than the simple result without considering the S-D mixing effect. Possible detecting channels are suggested and it is shown that psi(1P1) is able to be found with the accumulation of 30 million events of psi' at BEPC.Comment: 9-page RevTex file. Version for publication in Phys. Rev.

Quantum Theory of All-Optical Switching in Nonlinear Sagnac Interferometers

Recently, our group has demonstrated an ultrafast, low-loss, fiber-loop switch based on a nonlinear Sagnac-interferometer design, using which entangled photons were shown to be routed without any measurable degradation in their entanglement fidelity [Hall {\it et al.}, Phys. Rev. Lett. {\bf 106}, 053901 (2011)]. Such a device represents an enabling technology for a rich variety of networked quantum applications. In this paper we develop a comprehensive quantum theory for such switches in general, i.e., those based on nonlinear Sagnac interferometers, where the in-coupling of quantum noise is carefully modeled. Applying to the fiber-loop switch, the theory shows good agreement with the experimental results without using any fitting parameter. This theory can serve as an important guiding tool for configuring switches of this kind for future quantum networking applications.Comment: To appear in New J. Physic