The phase sensitivity of a fully quantum three-mode nonlinear interferometer

We study a nonlinear interferometer consisting of two consecutive parametric amplifiers, where all three optical fields (pump, signal and idler) are treated quantum mechanically, allowing for pump depletion and other quantum phenomena. The interaction of all three fields in the final amplifier leads to an interference pattern from which we extract the phase uncertainty. We find that the phase uncertainty oscillates around a saturation level that decreases as the mean number $N$ of input pump photons increases. For optimal interaction strengths, we also find a phase uncertainty below the shot-noise level and obtain a Heisenberg scaling $1/N$. This is in contrast to the conventional treatment within the parametric approximation, where the Heisenberg scaling is observed as a function of the number of down-converted photons inside the interferometer.Comment: 8 pages, 7 figure

An optic to replace space and its application towards ultra-thin imaging systems

Centuries of effort to improve imaging has focused on perfecting and combining lenses to obtain better optical performance and new functionalities. The arrival of nanotechnology has brought to this effort engineered surfaces called metalenses, which promise to make imaging devices more compact. However, unaddressed by this promise is the space between the lenses, which is crucial for image formation but takes up by far the most room in imaging systems. Here, we address this issue by presenting the concept of and experimentally demonstrating an optical 'spaceplate', an optic that effectively propagates light for a distance that can be considerably longer than the plate thickness. Such an optic would shrink future imaging systems, opening the possibility for ultra-thin monolithic cameras. More broadly, a spaceplate can be applied to miniaturize important devices that implicitly manipulate the spatial profile of light, for example, solar concentrators, collimators for light sources, integrated optical components, and spectrometers.Comment: 4 figures, 3 videos, includes complete S

Transparency, disclosure and the pricing of future earnings in the European market

Paper presented at "Accounting at a Tipping Point", the American Accounting Association (AAA) Annual Meeting held in New York City on August 1-5, 2009. Final version published in Journal of Business Finance and Accounting until title Accruals, Disclosure and the Pricing of Future Earnings in the European Market. Available online at http://onlinelibrary.wiley.com/The present study examines the role of disclosure in assisting market participants to form expectations of future earnings by observing the accrual content of reported earnings. Accounting research has been focusing on investigating the ability of accounting numbers and practices to provide relevant information to market participants. In the context of the association between market returns and accounting numbers or practices, conclusions can be only drawn on the effect of these numbers and practices at an average level of disclosure. Here it is shown that these conclusions can be significantly altered at varying levels of disclosure. Employing a sample of European firms and their Transparency and Disclosure ratings conducted by Standard and Poor’s, we show how disclosure and accruals jointly affect earnings expectations that are included in current stock returns. It is shown that both the joint effect of disclosure and accruals depends on the magnitude, sign and the nature of accruals (i.e. current and non-current accruals), and that increased disclosure appears to correct overstated expectations arising mostly from the extensive use of current accruals and negative non-current accruals

Etude de la transparence électromagnétiquement induite dans un ensemble d'atomes froids et application aux mémoires quantiques

Afin d'implémenter des protocoles de communications quantiques, comme cryptographie quantique par exemple, sur des distances supérieures à la centaine de kilomètres à l'aide de fibres optiques, il est nécessaire de développer de nouveaux outils : les répéteurs quantiques. Le principe de fonctionnement de ceux-ci repose sur l'existence de mémoires quantiques capable de stocker l'état de la lumière et de le réémettre à la demande. L'objectif de cette thèse est la réalisation d'une mémoire quantique dans un ensemble d'atomes froids de césium à l'aide d'un protocole de transparence électromagnétiquement induite (EIT). La première étape de ce travail a été la réalisation d'un piège magnéto-optique permettant de générer un nuage d'atomes froid de césium présentant une forte épaisseur optique. La seconde a été l'étude de la transparence du milieu. Ainsi, dans un système énergétique en , l'application d'un champ de contrôle sur la transition adjacente à celle du champ signal permet d'ouvrir une fenêtre de transparence. Deux phénomènes peuvent expliquer cette observation : l'EIT qui correspond à des interférences destructives entre les chemins d'excitation et la séparation Autler-Townes (ATS) qui implique la séparation du niveau excité en deux niveaux habillés. Une étude détaillé et quantitative des deux phénomènes a été réalisée. La dernière étape a été la démonstration du stockage d'un état cohérent en régime de photons uniques avec une efficacité de 24% ainsi que les premiers résultats du stockage d'un bit d'information quantique encodé dans le moment orbital angulaire de la lumière.In order to implement quantum communications, such as quantum cryptography, over distances larger than one hundred of kilometers using optical fibers, it is required to develop new tools known as "quantum repeaters". The way those devices work is based on the development of quantum memories which that store the quantum state of light and to retrieve it on demand. The goal of this Phd thesis is the realization of a quantum memory based on a cold atomic ensemble of cesium using a protocol Electromagnetically Induced Transparency (EIT). The first step of this work was the realization of a magneto-optical trap producing a cold atomic cloud of cesium exhibiting a large optical depth. The second step was the study of the transparency of the media. Indeed, in a energy scheme, the application of a control field on the nearby transition of the signal field results in opening a transparency window. Two phenomena can explain this observation : the EIT which corresponds to destructive interferences between various excitation paths and Autler-Townes Splitting (ATS) corresponding to the separation of the excited state into two dressed states. A quantitative and detailed study has been carried out. The last step was the demonstration of the storage a coherent state in the single photon regime with an efficiency of 24% and the preliminary results of the storage of a quantum information bit.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF