Universität Stuttgart

Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1

Browse

Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Institut für Theoretische Physik IStart date: 2020Author: search.filters.author.Lutz, Eric

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    ItemOpen Access
    A quantum heat engine driven by atomic collisions
    (2021) Bouton, Quentin; Nettersheim, Jens; Burgardt, Sabrina; Adam, Daniel; Lutz, Eric; Widera, Artur
    Quantum heat engines are subjected to quantum fluctuations related to their discrete energy spectra. Such fluctuations question the reliable operation of thermal machines in the quantum regime. Here, we realize an endoreversible quantum Otto cycle in the large quasi-spin states of Cesium impurities immersed in an ultracold Rubidium bath. Endoreversible machines are internally reversible and irreversible losses only occur via thermal contact. We employ quantum control to regulate the direction of heat transfer that occurs via inelastic spin-exchange collisions. We further use full-counting statistics of individual atoms to monitor quantized heat exchange between engine and bath at the level of single quanta, and additionally evaluate average and variance of the power output. We optimize the performance as well as the stability of the quantum heat engine, achieving high efficiency, large power output and small power output fluctuations.
  • Thumbnail Image
    ItemOpen Access
    Generalized Clausius inequalities in a nonequilibrium cold-atom system
    (2023) Mayer, Daniel; Lutz, Eric; Widera, Artur
    Thermodynamic inequalities, such as the Clausius inequality, characterize the direction of nonequilibrium processes. However, the latter result presupposes a system coupled to a heat bath that drives it to a thermal state. Far from equilibrium, the Clausius inequality can be generalized using information-theoretic quantities. For initially isolated systems that are moved from an equilibrium state by a dissipative heat exchange, the generalized Clausius inequality is predicted to be reversed. We here experimentally investigate the nonequilibrium thermodynamics of an initially isolated dilute gas of ultracold Cesium atoms that can be either thermalized or pushed out of equilibrium by means of laser cooling techniques. We determine in both cases the phase-space dynamics by tracing the evolution with position-resolved fluorescence imaging, from which we evaluate all relevant thermodynamic quantities. We confirm the validity of the generalized Clausius inequality for the first process and of the reversed generalized Clausius inequality for the second transformation.
  • Thumbnail Image
    ItemOpen Access
    Nonequilibrium thermodynamics of quantum coherence beyond linear response
    (2024) Rodrigues, Franklin L. S.; Lutz, Eric
    Quantum thermodynamics allows for the interconversion of quantum coherence and mechanical work. Quantum coherence is thus a potential physical resource for quantum machines. However, formulating a general nonequilibrium thermodynamics of quantum coherence has turned out to be challenging. In particular, precise conditions under which coherence is beneficial to or, on the contrary, detrimental for work extraction from a system have remained elusive. We here develop a generic dynamic-Bayesian-network approach to the far-from-equilibrium thermodynamics of coherence. We concretely derive generalized fluctuation relations and a maximum-work theorem that fully account for quantum coherence at all times, for both closed and open dynamics. We obtain criteria for successful coherence-to-work conversion, and identify a nonequilibrium regime where maximum work extraction is increased by quantum coherence for fast processes beyond linear response.
  • Thumbnail Image
    ItemOpen Access
    Electrostatic all-passive force clamping of charged nanoparticles
    (2025) Tuna, Yazgan; Al-Hiyasat, Amer; Kashkanova, Anna D.; Dechant, Andreas; Lutz, Eric; Sandoghdar, Vahid
    In the past decades, many techniques have been explored for trapping microscopic and nanoscopic objects, but the investigation of nano-objects under arbitrary forces and conditions remains nontrivial. One fundamental case concerns the motion of a particle under a constant force, known as force clamping . Here, we employ metallic nanoribbons embedded in a glass substrate in a capacitor configuration to generate a constant electric field on a charged nanoparticle in a water-filled glass nanochannel. We estimate the force fields from Brownian trajectories over several micrometers and confirm the constant behavior of the forces both numerically and experimentally. Furthermore, we manipulate the diffusion and relaxation times of the nanoparticles by tuning the charge density on the electrode. Our highly compact and controllable setting allows for the trapping and force-clamping of charged nanoparticles in a solution, providing a platform for investigating nanoscopic diffusion phenomena.