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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Institut für Theoretische Physik IIStart date: 2010End date: 2019Publication Type: search.filters.UBSTyp.Zeitschriftenartikel

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Now showing 1 - 5 of 5
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    Nonequilibrium sensing and its analogy to kinetic proofreading
    (2015) Hartich, David; Barato, Andre C.; Seifert, Udo
    For a paradigmatic model of chemotaxis, we analyze the effect of how a nonzero affinity driving receptors out of equilibrium affects sensitivity. This affinity arises whenever changes in receptor activity involve adenosine triphosphate hydrolysis. The sensitivity integrated over a ligand concentration range is shown to be enhanced by the affinity, providing a measure of how much energy consumption improves sensing. With this integrated sensitivity we can establish an intriguing analogy between sensing with nonequilibrium receptors and kinetic proofreading: the increase in integrated sensitivity is equivalent to the decrease of the error in kinetic proofreading. The influence of the occupancy of the receptor on the phosphorylation and dephosphorylation reaction rates is shown to be crucial for the relation between integrated sensitivity and affinity. This influence can even lead to a regime where a nonzero affinity decreases the integrated sensitivity, which corresponds to anti-proofreading.
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    Thermodynamics of micro- and nano-systems driven by periodic temperature variations
    (2015) Brandner, Kay; Saito, Keiji; Seifert, Udo
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    Functional integral approach to time-dependent heat exchange in open quantum systems : general method and applications
    (2015) Carrega, M.; Solinas, P.; Braggio, A.; Sassetti, M.; Weiß, Ulrich
    We establish the path integral approach for the time-dependent heat exchange of an externally driven quantum system coupled to a thermal reservoir. We derive the relevant influence functional and present an exact formal expression for the moment generating functional which carries all statistical properties of the heat exchange process for general linear dissipation. The method is applied to the time-dependent average heat transfer in the dissipative two-state system (TSS). We show that the heat can be written as a convolution integral which involves the population and coherence correlation functions of the TSS and additional correlations due to a polarization of the reservoir. The corresponding expression can be solved in the weak-damping limit both for white noise and for quantum mechanical coloured noise. The implications of pure quantum effects are discussed. Altogether a complete description of the dynamics of the average heat transfer ranging from the classical regime down to zero temperature is achieved.
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    Coherence-enhanced efficiency of feedback-driven quantum engines
    (2015) Brandner, Kay; Bauer, Michael; Schmid, Michael T.; Seifert, Udo
    A genuine feature of projective quantum measurements is that they inevitably alter the mean energy of the observed system if the measured quantity does not commute with the Hamiltonian. Compared to the classical case, Jacobs proved that this additional energetic cost leads to a stronger bound on the work extractable after a single measurement from a system initially in thermal equilibrium (2009 Phys. Rev. A 80 012322). Here, we extend this bound to a large class of feedback-driven quantum engines operating periodically and in finite time. The bound thus implies a natural definition for the efficiency of information to work conversion in such devices. For a simple model consisting of a laser-driven two-level system, we maximize the efficiency with respect to the observable whose measurement is used to control the feedback operations. We find that the optimal observable typically does not commute with the Hamiltonian and hence would not be available in a classical two level system. This result reveals that periodic feedback engines operating in the quantum realm can exploit quantum coherences to enhance efficiency.
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    Efficiencies of a molecular motor : a generic hybrid model applied to the F1-ATPase
    (2012) Zimmermann, Eva; Seifert, Udo
    In a single-molecule assay, the motion of a molecular motor is often inferred by measuring the stochastic trajectory of a large probe particle attached to it. We discuss a simple model for this generic setup taking into account explicitly the elastic coupling between the probe and the motor. The combined dynamics consists of discrete steps of the motor and the continuous Brownian motion of the probe. Motivated by recent experiments on the F1-ATPase, we investigated three types of efficiencies both in simulations and in a Gaussian approximation. Overall, we obtained good quantitative agreement with the experimental data. In particular, we clarify the conditions under which one of these efficiencies becomes larger than 1.