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[hal-02129630] Fast quantum control in dissipative systems using dissipationless solutions (5/16/19)

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[hal-02043030] Optimal work in a harmonic trap with bounded stiffness (4/29/19)

We apply Pontryagin's principle to drive rapidly a trapped overdamped Brownian particle in contact with a thermal bath between two equilibrium states corresponding to different trap stiffness $\kappa$. We work out the optimal time dependence $\kappa(t)$ by minimising the work performed on the particle under the non-holonomic constraint $0\leq\kappa\leq\kappa_{\max}$, an experimentally relevant situation. Several important differences arise, as compared with the case of unbounded stiffness that has been analysed in the literature. First, two arbitrary equilibrium states may not always be connected. Second, depending on the operating time $t_{\text{f}}$ and the desired compression ratio $\kappa_{\text{f}}/\kappa_{\text{\i}}$, different types of solutions emerge. Finally, the differences in the minimum value of the work brought about by the bounds may become quite large, which may have a relevant impact on the optimisation of heat engines.

[hal-01987485] Basin Entropy, a Measure of Final State Unpredictability and Its Application to the Chaotic Scattering of Cold Atoms (4/12/19)

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[hal-01945874] Phase transition kinetics for a Bose Einstein condensate in a periodically driven band system (4/12/19)

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[hal-01850268] Engineered Swift Equilibration for Brownian objects: from underdamped to overdamped dynamics (4/29/19)

We propose a general framework to study transformations that drive an underdamped Brownian particle in contact with a thermal bath from an equilibrium state to a new one in an arbitrarily short time. To this end, we make use of a time and space-dependent potential, that plays a dual role: confine the particle, and manipulate the system. In the special case of an isothermal compression or decompression of a harmonically trapped particle, we derive explicit protocols that perform this quick transformation, following an inverse engineering method. We focus on the properties of these protocols, which crucially depend on two key dimensionless numbers that characterize the relative values of the three timescales of the problem, associated with friction, oscillations in the confinement and duration of the protocol. In particular, we show that our protocols encompass the known overdamped version of this problem and extend it to any friction for decompression and to a large range of frictions for compression.

[hal-01787234] Robust calibration of an optical-lattice depth based on a phase shift (4/12/19)

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[hal-01695032] Thermal bath Engineering for Swift Equilibration (4/12/19)

We propose a new protocol that ensures the fast equilibration of an overdamped harmonic oscillator by a joint time-engineering of the confinement strength and of the effective temperature of the thermal bath. We demonstrate experimentally the effectiveness of our protocol with an optically trapped Brownian particle and report an equilibrium recovering time reduced by about two orders of magnitude compared to the natural relaxation time. Our scheme paves the way towards reservoir engineering in nano-systems.

Masques matériels nanométriques Condensats de Bose-Einstein Étude numérique Bose Einstein condensate Rubidium Beam splitter Réseau optique Tunnel Effect Fluorescence microscopy Condensation de bose-Einstein Phase space Periodic potentials Optical tweezers Espace des phases Condensat de Bose-Einstein Mirror-magneto-optical trap Nano-lithographie Optical molasses Plasmon polariton de surface Condensat Bose-Einstein Ultracold atoms Atomic beam Nano-lithography Bose-Einstein Semiclassical and variationnal approximation Mélasse optique Effet tunnel Bose-Einstein condensate Piège magnéto-optique à miroir Atom chip Self assembled monolayers Non-adiabatic regime Bose-Einstein Condensate Onde de matière Matter wave Bragg scattering Lentille de Fresnel Matter waves Puce atomique Couches mono-moléculaire auto assemblées Ouvertures métalliques sub-longueur d'onde Optical lattices Microscopie de fluorescence Césium Atom optics Cold atoms Sub-wavelength metallic apertures Surface plasmon polariton Bragg Diffraction Approximation semi-classique et variationnelle Condensation Diffraction de Bragg Supersymétrie en mécanique quantique Atom laser Optique atomique Bose Einstein Condensation Jet atomique Atomes froids Optical lattice Supersymmetry in quantum mechanics Réseaux Optiques Fresnel lens Maxwell's demon Transport optimal Chaos