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Palaiseau, France

Jonas A.,Koc University | Karadag Y.,Koc University | Mestre M.,Koc University | Mestre M.,Institute dOptique | Kiraz A.,Koc University
Journal of the Optical Society of America B: Optical Physics | Year: 2012

We report measurements of ultrahigh quality factors (Q-factors) of the optical whispering-gallery modes excited via a tapered optical-fiber waveguide in single glycerol-water microdroplets standing on a superhydrophobic surface in air. Owing to the high contact angle of the glycerol-water mixture on the superhydrophobic surface (≥155°), microdroplets with the geometry of a truncated sphere minimally distorted by gravity and contact line pinning effects could be generated. Q-factors up to 2.3 × 106 were observed for such droplets with radii of 100-200 μm exposed to the ambient atmosphere in a closed chamber with controlled relative humidity. Placement of microdroplets in a constant humidity environment permitted prolonged characterization of Q-factors for individual microdroplets. We found that the Q-factors in air were stable over more than 1 h and their measured values were limited mostly by the thermally induced droplet shape fluctuations. © 2012 Optical Society of America.

Gillett G.G.,Queensland University of Technology | Dalton R.B.,Queensland University of Technology | Lanyon B.P.,Queensland University of Technology | Almeida M.P.,Queensland University of Technology | And 7 more authors.
Physical Review Letters | Year: 2010

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario-the stabilization of nonorthogonal states of a qubit against dephasing-we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems. © 2010 The American Physical Society.

Jennewein T.,University of Waterloo | Jennewein T.,Queensland University of Technology | Jennewein T.,Austrian Academy of Sciences | Barbieri M.,Queensland University of Technology | And 2 more authors.
Journal of Modern Optics | Year: 2011

Photonics is a promising architecture for the realisation of quantum information processing, since the two-photon interaction, or non-linearity, necessary to build logical gates can efficiently be realised by the use of interference with ancillary photons and detection 1. Although single-photon sources and detectors are pivotal in realisations of such systems, clear guidelines for the required performance of realistic systems are yet to be defined. We present our detailed numerical simulation of several quantum optics circuits including sources and detectors all represented in multi-dimensional Fock-spaces, which allows us to obtain experimentally realistic performance bounds for these devices. In addition, the single-photon source based on switched parametric down-conversion is studied, which in principle could reach the required performance. Three approaches for implementing the switching hierarchy of the photons are simulated, and their anticipated performance is obtained. Our results define the bar for the optical devices needed to achieve the first level of linear-optics quantum computing outside the coincidence basis. © 2011 Taylor & Francis.

Hebert M.,Jean Monnet University | Hebert M.,Institute dOptique
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The well-known Yule-Nielsen modified spectral Neugebauer model is one of the most accurate predictive models for the spectral reflectance of printed halftone colors which expresses the spectral reflectance of halftones raised to the power 1/n as a linear combination of the spectral reflectance of the fulltone colors (Neugebauer primaries) also raised to the power 1/n, where n is a tunable real number. The power 1/n transform, characteristic of the Yule-Nielsen transform, empirically models the nonlinear relationship between the spectral reflectances of halftones and fulltones due to the internal propagation of light by scattering into the printing support, a phenomenon known as "optical dot gain" or "Yule-Nielsen effect". In this paper, we propose a graphical method permitting to observe this non-linear relationship in the case of single-ink halftones and to experimentally check the capacity of the Yule-Nielsen model to predict it accurately. In the case where the Yule-Nielsen transform is not well adapted to the considered type of prints, we propose alternative transforms in order to improve the prediction accuracy. © 2014 SPIE-IS&T.

Aspect A.,Institute dOptique
Proceedings of the 25th Solvay Conference on Physics: The Theory of the Quantum World | Year: 2013

I ask the question: What can we infer about the nature and structure of the physical world (a) from experiments already done to test the predictions of quantum mechanics (b) from the assumption that all future experiments will agree with those predictions? I discuss existing and projected experiments related to the two classic paradoxes of quantum mechanics, named respectively for EPR and Schrödinger's Cat, and show in particular that one natural conclusion from both types of experiment implies the abandonment of the concept of macroscopic counterfactual definiteness.

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