Professor Ian Walmsley CBE FRS FCGI

Abstract:

We propose a novel experimental technique based on the process of parametric downconversion for the generation of photon pairs characterized by ultra-high dimensional spectral entanglement. It is shown that a superlattice of nonlinear and linear segments can be exploited to obtain states exhibiting a remarkably large entanglement, with a Schmidt number in the region of 10(7). We furthermore consider the application of such highly entangled photon pairs for the violation of a Bell inequality constructed from a measurement of the transverse wavevector Wigner function; such an approach eliminates the need for filtering the photon pairs and consequently eliminates an important potential loophole.

Abstract:

We analyze a quantum optical memory based on the off-resonant Raman interaction of a single broadband photon, copropagating with a classical control pulse, with an atomic ensemble. The conditions under which the memory can perform optimally are found, by means of a universal mode decomposition. This enables the memory efficiency to be specified in terms of a single parameter, and the control field pulse shape to be determined via a simple nonlinear scaling. We apply the same decomposition to determine the optimal configurations for read-out. © 2007 The American Physical Society.