Ian Walmsley

Abstract:

We have investigated the intensity dependence of high-order harmonic generation in argon when the two shortest quantum paths contribute to the harmonic emission. For the first time to our knowledge, experimental conditions were found to clearly observe interference between these two quantum paths that are in excellent agreement with theoretical predictions. This result is a first step towards the direct experimental characterization of the full single-atom dipole moment and demonstrates an unprecedented accuracy of quantum path control on an attosecond time scale.

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.