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Optimal control is a valuable tool for quantum simulation, allowing for the optimized preparation, manipulation, and measurement of quantum states. Through the optimization of a time-dependent control parameter, target states can be prepared to initialize or engineer specific quantum dynamics. In this work, we focus on the tailoring of a unitary evolution leading to the stroboscopic stabilization of quantum states of a Bose-Einstein condensate in an optical lattice. We show how, for states with space and time symmetries, such an evolution can be derived from the initial state-preparation controls; while for a general target state we make use of quantum optimal control to directly generate a stabilizing Floquet operator. Numerical optimizations highlight the existence of a quantum speed limit for this stabilization process, and our experimental results demonstrate the efficient stabilization of a broad range of quantum states in the lattice.
Control of stochastic systems is a challenging open problem in statistical physics, with potential applications in a wealth of systems from biology to granulates. Unlike most cases investigated so far, we aim here at controlling a genuinely out-of-equilibrium system, the two dimensional Active Brownian Particles model in a harmonic potential, a paradigm for the study of self-propelled bacteria. We search for protocols for the driving parameters (stiffness of the potential and activity of the particles) bringing the system from an initial passive-like stationary state to a final active-like one, within a chosen time interval. The exact analytical results found for this prototypical system of self-propelled particles brings control techniques to a wider class of out-of-equilibrium systems.
We discuss the emulation of non-Hermitian dynamics during a given time window using a low-dimensional quantum system coupled to a finite set of equidistant discrete states acting as an effective continuum. We first emulate the decay of an unstable state and map the quasi-continuum parameters, enabling the precise approximation of non-Hermitian dynamics. The limitations of this model, including in particular short- and long-time deviations, are extensively discussed. We then consider a driven two-level system and establish criteria for non-Hermitian dynamics emulation with a finite quasi-continuum. We quantitatively analyze the signatures of the finiteness of the effective continuum, addressing the possible emergence of non-Markovian behavior during the time interval considered. Finally, we investigate the emulation of dissipative dynamics using a finite quasi-continuum with a tailored density of states. We show through the example of a two-level system that such a continuum can reproduce non-Hermitian dynamics more efficiently than the usual equidistant quasi-continuum model.
We report on the design of a Hamiltonian ratchet exploiting periodically at rest integrable trajectories in the phase space of a modulated periodic potential, leading to the linear non-diffusive transport of particles. Using Bose-Einstein condensates in a modulated one-dimensional optical lattice, we make the first observations of this spatial ratchet, which provides way to coherently transport matter waves with possible applications in quantum technologies. In the semiclassical regime, the quantum transport strongly depends on the effective Planck constant due to Floquet state mixing. We also demonstrate the interest of quantum optimal control for efficient initial state preparation into the transporting Floquet states to enhance the transport periodicity.
We report on speeding-up equilibrium recovery in the previously unexplored general case of the underdamped regime using an optically levitated particle. We accelerate the convergence toward equilibrium by an order of magnitude compared to the natural relaxation time. We then discuss the efficiency of the studied protocols, especially for a multidimensional system. These results pave the way for optimizing realistic nanomachines with application to sensing and developing efficient nanoheat engines.
Sujets
Gaz quantiques
Rubidium
Optical molasses
Atomes froids
Optique atomique
Collisions ultrafroides
Mélasse optique
Bose Einstein Condensation
Atom chip
Condensats de Bose– Einstein
Condensats de Bose-Einstein
Piège magnéto-optique à miroir
Dynamical tunneling
Théorie de Floquet
Atomic beam
Condensats de Bose Einstein
Masques matériels nanométriques
Ouvertures métalliques sub-longueur d'onde
Diffraction de Bragg
Contrôle optimal
Ultracold atoms
Quantum optimal control
Bose-Einstein
Chaos-assisted tunneling
Lentille de Fresnel
Bose-Einstein Condensate
Physique quantique
Condensat Bose-Einstein
Non-adiabatic regime
Entropy production
Simulation quantique
Mirror-magneto-optical trap
Floquet theory
Semiclassical and variationnal approximation
Bose-Einstein condensates Coherent control Cold atoms and matter waves Cold gases in optical lattices
Maxwell's demon
Optimal control theory
Periodic potentials
Quantum simulator
Levitodynamics
Quantum control
Quantum gases
Ratchet effect
Condensation
Gaz quantique
Espace des phases
Quantum physics
Chaos quantique
Onde de matière
Bragg scattering
Effet tunnel
Optical lattices
Réseaux Optiques
Phase space
Engineering
Atomes ultrafroids dans un réseau optique
Atom optics
Contrôle optimal quantique
Quantum chaos
Field equations stochastic
Fluorescence microscopy
Couches mono-moléculaire auto assemblées
Matter waves
Approximation semi-classique et variationnelle
Césium
Chaos
Bose-Einstein condensate
Bose–Einstein condensates
Nano-lithography
Cold atoms
Beam splitter
Fluid
Réseau optique
Bose Einstein condensate
Condensat de Bose-Einstein
Optical lattice
Bose-Einstein condensates
Quantum gas
Quantum simulation
Réseaux optiques
Nano-lithographie
Puce atomique
Microscopie de fluorescence
Effet tunnel dynamique
Bragg Diffraction
Simulateur quantique
Bose-Einstein Condensates
Matter wave
Effet rochet
Optical tweezers
Initial state
Self assembled monolayers
Quantum collisions
Hamiltonian
Jet atomique
Fresnel lens
Effet tunnel assisté par le chaos
Condensation de bose-Einstein
Plasmon polariton de surface
Atom laser