Ressources quantiques et traitement numérique des images

Ressources quantiques et traitement numérique des images

Quantum image coding with a reference-frame-independent scheme

For binary images, or bit planes of non-binary images, we investigate the possibility of a quantum coding decodable by a receiver in the absence of reference frames shared with the emitter. Direct image coding with one qubit per pixel and non-aligned frames leads to decoding errors equivalent to a quantum bit-flip noise increasing with the misalignment. We show the feasibility of frame-invariant coding by using for each pixel a qubit pair prepared in one of two controlled entangled states. With just one common axis shared between the emitter and receiver, exact decoding for each pixel can be obtained by means of two two-outcome projective measurements operating separately on each qubit of the pair. With strictly no alignment information between the emitter and receiver, exact decoding can be obtained by means of a two-outcome projective measurement operating jointly on the qubit pair. In addition, the frame-invariant coding is shown much more resistant to quantum bit-flip noise compared to the direct non-invariant coding. For a cost per pixel of two (entangled) qubits instead of one, complete frame-invariant image coding and enhanced noise resistance are thus obtained

Revisiting SIFT for plant foliage in RGB images acquired on a turntable

In this work, SIFT features are revisited for their use in two applications of computer vision for plant analysis. The first application is the reconstruction of 3D models of plants through tracking homologue points in successive intensity images. The second application is to provide a new global descriptor that gives a measure of the level of self-similariy of foliage for plants of different architectures and foliar appearance. In order to properly exploit SIFT descriptors in relation to these applications, we discuss two aspects of the classical SIFT keypoint matching practice. On the one hand we propose to match detected keypoints based on a scale criterion. On the other hand, we drop the ratio rule while matching keypoints in two images and propose the use of a spatial proximity filter instead

Entropie de von Neumann et information de Holevo pour le signal quantique en présence de bruit

Entropie de von Neumann et information de Holevo pour le signal quantique en présence de bruit

Stochastic antiresonance in qubit phase estimation with quantum thermal noise

We consider the fundamental quantum information processing task consisting in estimating the phase of a qubit. Following quantum measurement, the estimation performance is evaluated by the classical Fisher information which determines the best performance limiting any estimator and achievable by the maximum likelihood estimator. Estimation is analyzed in the presence of decoherence represented by a quantum thermal noise at arbitrary temperature. As the noise temperature is increased, we show the possibility of nontrivial behaviors of decoherence, with an estimation performance which does not necessarily degrade uniformly, but can experience nonmonotonic evolutions. Regimes are found where higher noise temperatures turn more favorable to estimation. Such behaviors are related to stochastic resonance or antiresonance effects, where noise reveals beneficial to information processing

Modèle stochastique et représentation par graphe pour le suivi spatio-temporel de pathogènes à la surface de feuilles par imagerie

Modèle stochastique et représentation par graphe pour le suivi spatio-temporel de pathogènes à la surface de feuilles par imagerie

L’intrication en imagerie quantique pour résister au bruit

L’intrication en imagerie quantique pour résister au bruit