Ian Walmsley

Abstract:

The certificate of success for a number of important quantum information processing protocols, such as entanglement distillation, is based on the difference in the entanglement content of the system quantum states before and after the protocol. In such cases, effective bounds need to be placed on the entanglement of non-local states consistent with statistics obtained from local measurements. In this paper, we study numerically the ability of a hybrid homodyne detector that combines phase sensitivity and photon-number resolution to set accurate bounds on the entanglement content of two-mode quadrature squeezed states without the need for full state tomography. We show that it is possible to set tight lower bounds on the entanglement of a family of two-mode degaussified states using only a few measurements. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Abstract:

We demonstrate the coherent storage and retrieval of sub-nanosecond low-intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium vapor, using the novel, far offresonant two-photon Raman memory protocol. © 2010 Optical Society of America.

Abstract:

Given an experimental set-up and a fixed number of measurements, how should one take data in order to optimally reconstruct the state of a quantum system? We show how to calculate the optimal design explicitly. © 2010 Optical Society of America.

Abstract:

We present a direct UV-written integrated photonic circuit with on-chip phase control through a thermo-optic phase shifter. An arbitrary beam splitter and a two-photon NOON state are demonstrated with high visibility interference. © 2010 Optical Society of America.