Quantum limits in image processing

We determine the bound to the maximum achievable sensitivity in the estimation of a scalar parameter from the information contained in an optical image in the presence of quantum noise. This limit, based on the Cramer-Rao bound, is valid for any image processing protocol. It is calculated both in the case of a shot noise limited image and of a non-classical illumination. We also give practical experimental implementations allowing us to reach this absolute limit.Comment: 4 pages, two figure

Quantum measurements of spatial conjugate variables: Displacement and tilt of a Gaussian beam

We consider the problem of measurement of optical transverse profile parameters and their conjugate variable. Using multi-mode analysis, we introduce the concept of detection noise-modes. For Gaussian beams, displacement and tilt are a pair of transverse profile conjugate variables. We experimentally demonstrate their optimal encoding and detection with a spatial homodyning scheme. Using higher order spatial mode squeezing, we show the sub-shot noise measurements for the displacement and tilt of a Gaussian beam.Comment: 3 page

A quantum study of multi-bit phase coding for optical storage

We propose a scheme which encodes information in both the longitudinal and spatial transverse phases of a continuous-wave optical beam. A split detector-based interferometric scheme is then introduced to optimally detect both encoded phase signals. In contrast to present-day optical storage devices, our phase coding scheme has an information storage capacity which scales with the power of the read-out optical beam. We analyse the maximum number of encoding possibilities at the shot noise limit. In addition, we show that using squeezed light, the shot noise limit can be overcome and the number of encoding possibilities increased. We discuss a possible application of our phase coding scheme for increasing the capacities of optical storage devices.Comment: 8 pages, 7 figures (Please email author for a PDF file if the manuscript does not turn out properly

TEM10 homodyne detection as an optimal small displacement and tilt measurements scheme

We report an experimental demonstration of optimal measurements of small displacement and tilt of a Gaussian beam - two conjugate variables - involving a homodyne detection with a TEM10 local oscillator. We verify that the standard split detection is only 64% efficient. We also show a displacement measurement beyond the quantum noise limit, using a squeezed vacuum TEM10 mode within the input beam.Comment: 9 pages, 8 figure

Optimum Small Optical Beam Displacement Measurement

We derive the quantum noise limit for the optical beam displacement of a TEM00 mode. Using a multimodal analysis, we show that the conventional split detection scheme for measuring beam displacement is non-optimal with 80% efficiency. We propose a new displacement measurement scheme that is optimal for small beam displacement. This scheme utilises a homodyne detection setup that has a TEM10 mode local oscillator. We show that although the quantum noise limit to displacement measurement can be surpassed using squeezed light in appropriate spatial modes for both schemes, the TEM10 homodyning scheme out-performs split detection for all values of squeezing.Comment: 13 pages, 7 figure

Imagerie quantique à petit nombre de modes transverses

Spatial multi-mode quantum optics, also termed « quantum imaging », allows a study of the detection of any physical parameter within an optical image. The parameter considered here can for instance be the transverse displacement or the tilt of a laser beam, or even the bit sequence of an optical disc encoded onto the beam.Such measurements are ultimately limited by the quantum nature of optical images. We show that the use of non classical beams allows a reduction of the measurement fluctuations below the latter fundamental limit.Using this theoretical result, we have performed optimal measurements of laser beam nano-displacement, as well as entanglement between this quantity and its conjugate variable : beam tilt. The implementation of these experiments has led us to demonstrate all the key elements required for quantum imaging experiments.We have also investigated the possibility of using multi-mode light as parallel communication channels for quantum information.L'optique quantique multi-mode spatiale, encore appelée « imagerie quantique », permet d'étudier la détection d'un paramètre physique quelconque au sein d'une image optique. Nous considérons en particulier la mesure de déplacement transverse d'un faisceau laser et la détection d'une séquence de bits gravée sur un disque optique. De telles mesures sont ultimement limitées par la nature quantique de l'image optique considérée. Néanmoins, l'utilisation d'un faisceau non classique permet de réduire les fluctuations de mesure sous cette limite fondamentale. A ce titre, nous présentons des mesures de nano-déplacements d'un faisceau laser, ainsi que l'intrication des variables conjuguées : position et inclinaison du faisceau. Ces expériences nous ont amenés à introduire l'ensemble des composants élémentaires requis en imagerie quantique.L'utilisation de lumière multi-mode comme support multi-canal d'information quantique est également détaillée

Quantum imaging with a small number of transverse modes

L'optique quantique multi-mode spatiale, encore appelée imagerie quantique , permet d étudier la détection d'un paramètre physique quelconque au sein d'une image optique. Nous considérons en particulier la mesure de déplacement transverse d'un faisceau laser et la détection d une séquence de bits gravée sur un disque optique. De telles mesures sont ultimement limitées par la nature quantique de l image optique considérée. Néanmoins, l utilisation d un faisceau non classique permet de réduire les fluctuations de mesure sous cette limite fondamentale. A ce titre, nous présentons des mesures de nano-déplacements d un faisceau laser, ainsi que l intrication des variables conjuguées : position et inclinaison du faisceau. Ces expériences nous ont amenés à introduire l ensemble des composants élémentaires requis en imagerie quantique. L'utilisation de lumière multi-mode comme support multi-canal dinformation quantique est également détaillée.Spatial multi-mode quantum optics, also termed "quantum imaging ", allows a study of the detection of any physical parameter within an optical image. The parameter considered here can for instance be the transverse displacement or the tilt of a laser beam, or even the bit sequence of an optical disc encoded onto the beam. Such measurements are ultimately limited by the quantum nature of optical images. We show that the use of non classical beams allows a reduction of the measurement ůctuations below the latter fundamental limit. Using this theoretical result, we have performed optimal measurements of laser beam nano-displacement, as well as entanglement between this quantity and its conjugate vari- able : beam tilt. The implementation of these experiments has led us to demonstrate all the key elements required for quantum imaging experiments. We have also investigated the possibility of using multi-mode light as parallel commu- nication channels for quantum information.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceAustraliaFRA