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Procédé de mesure de la force d’interaction entre une portion et une pointe d’une sonde de force d’un AFM solidaire d’un moyen d’excitation, le moyen d’excitation étant apte à vibrer en fonction d’un signal d’excitation e(t), le procédé comprenant une étape de mise en excitation de la sonde de force, un signal d’excitation étant appliqué configuré pour engendrer, une déflexion libre s0(t) formant un signal sinusoïdal modulé en amplitude par une impulsion, la sonde de force entrant en résonance à une fréquence de résonance libre f_0, une étape de mesure de la déflexion s(t), la sonde de force entrant en résonance à une fréquence de résonance d’interaction f_T, une étape de traitement dans laquelle est évalué un décalage fréquentiel Δf_T, différence entre la fréquence de résonance d’interaction de la sonde de force, et la fréquence de résonance libre.

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The effective control of atomic coherence with cold atoms has made atom interferometry an essential tool for quantum sensors and precision measurements. The performance of these interferometers is closely related to the operation of large wave packet separations. We present here a novel approach for atomic beam splitters based on the stroboscopic stabilization of quantum states in an accelerated optical lattice. The corresponding Floquet state is generated by optimal control protocols. In this way, we demonstrate an unprecedented Large Momentum Transfer (LMT) interferometer, with a momentum separation of 600 photon recoils ($600\hbar k$) between its two arms. Each LMT beam splitter is realized in a remarkably short time (2 ms) and is highly robust against the initial velocity dispersion of the wave packet and lattice depth fluctuations. Our study shows that Floquet engineering is a promising tool for exploring new frontiers in quantum physics at large scales, with applications in quantum sensing and testing fundamental physics.

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We numerically study the optimal control of an atomic Bose-Einstein condensate in an optical lattice. We present two generalizations of the gradient-based algorithm, GRAPE, in the non-linear case and for a two-dimensional lattice. We show how to construct such algorithms from Pontryagin’s maximum principle. A wide variety of target states can be achieved with high precision by varying only the laser phases setting the lattice position. We discuss the physical relevance of the different results and the future directions of this work.

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Microscopically probing quantum many-body systems by resolving their constituent particles is essential for understanding quantum matter. In most physical systems, distinguishing individual particles, such as electrons in solids, or neutrons and quarks in neutron stars, is impossible. Atombased quantum simulators offer a unique platform that enables the imaging of each particle in a many-body system. Until now, however, this capability has been limited to quantum systems in discretized space such as optical lattices and tweezers, where spatial degrees of freedom are quantized. Here, we introduce a novel method for imaging atomic quantum many-body systems in the continuum, allowing for in situ resolution of every particle. We demonstrate the capabilities of our approach on a two-dimensional atomic Fermi gas. We probe the density correlation functions, resolving their full spatial functional form, and reveal the shape of the Fermi hole arising from Pauli exclusion as a function of temperature. Our method opens the door to probing strongly-correlated quantum gases in the continuum with unprecedented spatial resolution, providing in situ access to spatially resolved correlation functions of arbitrarily high order across the entire system.

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In the absence of external forcing, all trajectories on the phase plane of the van der Pol oscillator tend to a closed, periodic, trajectory -- the limit cycle -- after infinite time. Here, we drive the van der Pol oscillator with an external time-dependent force to reach the limit cycle in a given finite time. Specifically, we are interested in minimising the non-conservative contribution to the work when driving the system from a given initial point on the phase plane to any final point belonging to the limit cycle. There appears a speed limit inequality, which expresses a trade-off between the connection time and cost -- in terms of the non-conservative work. We show how the above results can be { generalized to the broader family of non-linear oscillators given by} the Liénard equation. Finally, we also look into the problem of minimising the total work done by the external force.

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Sujets

Bragg Diffraction Gaz quantique Quantum control Condensation de bose-Einstein Condensats de Bose Einstein Quantum chaos Atom optics Lentille de Fresnel Quantum Ultracold atoms Condensat de Bose-Einstein Onde de matière Mechanics Beam splitter Chaos Contrôle optimal Bragg scattering Initial state Effet tunnel Dynamical tunneling Bose-Einstein condensate Phase space Masques matériels nanométriques Optical tweezers Cold atoms Constraint Jet atomique Mirror-magneto-optical trap Approximation semi-classique et variationnelle Espace des phases Lattice Field equations stochastic Current Bose-Einstein Condensate Piège magnéto-optique à miroir Electromagnetic field Physique quantique Quantum collisions Condensats de Bose– Einstein Time dependence Atomes ultrafroids dans un réseau optique Collisions ultrafroides Atom chip Experimental results Condensation Bose-Einstein condensates Mélasse optique Floquet theory Maxwell's demon Bose-Einstein Quantum optimal control Hamiltonian Bose–Einstein condensates Optical molasses Effet rochet Gaz quantiques Optimal control theory Diffraction de Bragg Puce atomique Théorie de Floquet Bose-Einstein Condensates Plasmon polariton de surface Bose-Einstein condensates Coherent control Cold atoms and matter waves Cold gases in optical lattices Réseaux optiques Matter wave Optical lattice Fluid Fresnel lens Atomes froids Ouvertures métalliques sub-longueur d'onde Bose Einstein condensate Césium Contrôle optimal quantique Optical lattices Condensats de Bose-Einstein Matter waves Levitodynamics Nano-lithography Bose Einstein Condensation Optique atomique Periodic potentials Microscopie de fluorescence Atomic beam Chaos-assisted tunneling Condensat Bose-Einstein Numerical methods Fluorescence microscopy Couches mono-moléculaire auto assemblées Atom laser Entropy production Engineering Non-adiabatic regime Réseau optique Effet tunnel assisté par le chaos Dimension Optical Chaos quantique Nano-lithographie Effet tunnel dynamique

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47

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82