Professor Ian Walmsley CBE FRS FCGI: Publications

Efficient optical implementation of the Bernstein-Vazirani algorithm - art. no. 010302

PHYSICAL REVIEW A 69:1 (2004) ARTN 010302

Authors:

P Londero, C Dorrer, M Anderson, S Wallentowitz, K Banaszek, IA Walmsley

Yield and temporal characterization of high-order harmonics from intense midinfrared excitation of a cesium vapor - art. no. 033807

PHYSICAL REVIEW A 69:3 (2004) ARTN 033807

Authors:

TO Clatterbuck, C Lyngå, PM Paul, LF DiMauro, MB Gaarde, KJ Schafer, P Agostini, KC Kulander, I Walmsley

Fiber-assisted detection with photon number resolution.

Opt Lett 28:23 (2003) 2387-2389

Authors:

Daryl Achilles, Christine Silberhorn, Cezary Sliwa, Konrad Banaszek, Ian A Walmsley

Abstract:

We report the development of a photon-number-resolving detector based on a fiber-optical setup and a pair of standard avalanche photodiodes. The detector is capable of resolving individual photon numbers and operates on the well-known principle by which a single-mode input state is split into a large number (eight) of output modes. We reconstruct the photon statistics of weak coherent input light from experimental data and show that there is a high probability of inferring the input photon number from a measurement of the number of detection events on a single run.

Photon engineering for quantum information processing

QUANTUM INFORM COMPU 3 (2003) 480-502

Authors:

AB U'Ren, K Banaszek, IA Walmsley

Abstract:

We study distinguishing information in the context of quantum interference involving more than one parametric downconversion (PDC) source and in the context of generating polarization-entangled photon pairs based on PDC. We arrive at specific design criteria for two-photon sources so that when used as part of complex optical systems, such as photon-based quantum information processing schemes, distinguishing information between the photons is eliminated guaranteeing high visibility interference. We propose practical techniques which lead to suitably engineered two-photon states that can be realistically implemented with available technology. Finally, we study an implementation of the nonlinear-sign shift (NS) logic gate with PDC sources and show the effect of distinguishing information on the performance of the gate.

Direct measurement of the spatial Wigner function with area-integrated detection.

Opt Lett 28:15 (2003) 1317-1319

Authors:

Eran Mukamel, Konrad Banaszek, Ian A Walmsley, Christophe Dorrer

Abstract:

We demonstrate experimentally a novel technique for characterizing transverse spatial coherence by using the Wigner distribution function. The method is based on the measurement of interference between a pair of rotated and displaced replicas of the input beam with an area-integrating detector, and it provides an optimal signal-to-noise ratio in regimes when array detectors are not available. We analyze the quantum-optical picture of the presented measurement for single-photon signals and discuss possible applications in quantum information processing.

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