@misc{MohammadyAuffevesAnders2020, author = {Mohammady, M. Hamed and Auff{\`e}ves, Alexia and Anders, Janet}, title = {Energetic footprints of irreversibility in the quantum regime}, series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1}, issn = {1866-8372}, doi = {10.25932/publishup-51676}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-516766}, pages = {16}, year = {2020}, abstract = {In classical thermodynamic processes the unavoidable presence of irreversibility, quantified by the entropy production, carries two energetic footprints: the reduction of extractable work from the optimal, reversible case, and the generation of a surplus of heat that is irreversibly dissipated to the environment. Recently it has been shown that in the quantum regime an additional quantum irreversibility occurs that is linked to decoherence into the energy basis. Here we employ quantum trajectories to construct distributions for classical heat and quantum heat exchanges, and show that the heat footprint of quantum irreversibility differs markedly from the classical case. We also quantify how quantum irreversibility reduces the amount of work that can be extracted from a state with coherences. Our results show that decoherence leads to both entropic and energetic footprints which both play an important role in the optimization of controlled quantum operations at low temperature. In classical thermodynamics irreversibility occurs whenever a non-thermal system is brought into contact with a thermal environment. Using quantum trajectories the authors here establish two energetic footprints of quantum irreversible processes, and find that while quantum irreversibility leads to the occurrence of a quantum heat and a reduction of work production, the two are not linked in the same manner as the classical laws of thermodynamics would dictate.}, language = {en} } @article{MohammadyAuffevesAnders2020, author = {Mohammady, M. Hamed and Auff{\`e}ves, Alexia and Anders, Janet}, title = {Energetic footprints of irreversibility in the quantum regime}, series = {Communications Physics}, volume = {3}, journal = {Communications Physics}, number = {1}, publisher = {Springer Nature}, address = {London}, issn = {2399-3650}, doi = {10.1038/s42005-020-0356-9}, pages = {1 -- 14}, year = {2020}, abstract = {In classical thermodynamic processes the unavoidable presence of irreversibility, quantified by the entropy production, carries two energetic footprints: the reduction of extractable work from the optimal, reversible case, and the generation of a surplus of heat that is irreversibly dissipated to the environment. Recently it has been shown that in the quantum regime an additional quantum irreversibility occurs that is linked to decoherence into the energy basis. Here we employ quantum trajectories to construct distributions for classical heat and quantum heat exchanges, and show that the heat footprint of quantum irreversibility differs markedly from the classical case. We also quantify how quantum irreversibility reduces the amount of work that can be extracted from a state with coherences. Our results show that decoherence leads to both entropic and energetic footprints which both play an important role in the optimization of controlled quantum operations at low temperature. In classical thermodynamics irreversibility occurs whenever a non-thermal system is brought into contact with a thermal environment. Using quantum trajectories the authors here establish two energetic footprints of quantum irreversible processes, and find that while quantum irreversibility leads to the occurrence of a quantum heat and a reduction of work production, the two are not linked in the same manner as the classical laws of thermodynamics would dictate.}, language = {en} } @article{EerqingSubramanianRubioJimenezetal.2021, author = {Eerqing, Narima and Subramanian, Sivaraman and Rubio Jimenez, Jesus and Lutz, Tobias and Wu, Hsin-Yu and Anders, Janet and Soeller, Christian and Vollmer, Frank}, title = {Comparing transient oligonucleotide hybridization kinetics using DNA-PAINT and optoplasmonic single-molecule sensing on gold nanorods}, series = {ACS photonics / American Chemical Society}, volume = {8}, journal = {ACS photonics / American Chemical Society}, number = {10}, publisher = {American Chemical Society}, address = {Washington}, issn = {2330-4022}, doi = {10.1021/acsphotonics.1c01179}, pages = {2882 -- 2888}, year = {2021}, abstract = {We report a comparison of two photonic techniques for single-molecule sensing: fluorescence nanoscopy and optoplasmonic sensing. As the test system, oligonucleotides with and without fluorescent labels are transiently hybridized to complementary "docking" strands attached to gold nanorods. Comparing the measured single-molecule kinetics helps to examine the influence of the fluorescent labels as well as factors arising from different sensing geometries. Our results demonstrate that DNA dissociation is not significantly altered by the fluorescent labels and that DNA association is affected by geometric factors in the two techniques. These findings open the door to exploiting plasmonic sensing and fluorescence nanoscopy in a complementary fashion, which will aid in building more powerful sensors and uncovering the intricate effects that influence the behavior of single molecules.}, language = {en} } @article{ScaliAndersCorrea2021, author = {Scali, Stefano and Anders, Janet and Correa, Luis A.}, title = {Local master equations bypass the secular approximation}, series = {Quantum : the open journal for quantum science}, volume = {5}, journal = {Quantum : the open journal for quantum science}, publisher = {Verein zur F{\"o}rderung des Open Access Publizierens in den Quantenwissenschaften}, address = {Wien}, issn = {2521-327X}, doi = {10.22331/q-2021-05-01-451}, pages = {24}, year = {2021}, abstract = {Master equations are a vital tool to model heat flow through nanoscale thermodynamic systems. Most practical devices are made up of interacting subsystems and are often modelled using either local master equations (LMEs) or global master equations (GMEs). While the limiting cases in which either the LME or the GME breaks down are well understood, there exists a 'grey area' in which both equations capture steady-state heat currents reliably but predict very different transient heat flows. In such cases, which one should we trust? Here we show that, when it comes to dynamics, the local approach can be more reliable than the global one for weakly interacting open quantum systems. This is due to the fact that the secular approximation, which underpins the GME, can destroy key dynamical features. To illustrate this, we consider a minimal transport setup and show that its LME displays exceptional points (EPs). These singularities have been observed in a superconducting-circuit realisation of the model [1]. However, in stark contrast to experimental evidence, no EPs appear within the global approach. We then show that the EPs are a feature built into the Redfield equation, which is more accurate than the LME and the GME. Finally, we show that the local approach emerges as the weak-interaction limit of the Redfield equation, and that it entirely avoids the secular approximation.}, language = {en} } @article{NematiHenkelAnders2022, author = {Nemati, Somayyeh and Henkel, Carsten and Anders, Janet}, title = {Coupling function from bath density of states}, series = {epl : a letters journal exploring the frontiers of physics}, volume = {139}, journal = {epl : a letters journal exploring the frontiers of physics}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0295-5075}, doi = {10.1209/0295-5075/ac7b42}, pages = {7}, year = {2022}, abstract = {Modelling of an open quantum system requires knowledge of parameters that specify how it couples to its environment. However, beyond relaxation rates, realistic parameters for specific environments and materials are rarely known. Here we present a method of inferring the coupling between a generic system and its bosonic (e.g., phononic) environment from the experimentally measurable density of states (DOS). With it we confirm that the DOS of the well-known Debye model for three-dimensional solids is physically equivalent to choosing an Ohmic bath. We further match a real phonon DOS to a series of Lorentzian coupling functions, allowing us to determine coupling parameters for gold, yttrium iron garnet (YIG) and iron as examples. The results illustrate how to obtain material-specific dynamical properties, such as memory kernels. The proposed method opens the door to more accurate modelling of relaxation dynamics, for example for phonon-dominated spin damping in magnetic materials.}, language = {en} } @article{FischerAndersSaalfrank2022, author = {Fischer, Eric Wolfgang and Anders, Janet and Saalfrank, Peter}, title = {Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {156}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {15}, publisher = {American Institute of Physics}, address = {Melville, NY}, issn = {0021-9606}, doi = {10.1063/5.0076434}, pages = {16}, year = {2022}, abstract = {It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under "ordinary" reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single-cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born-Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrodinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency omega(c) is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well.}, language = {en} } @article{HolmesAndersMintert2020, author = {Holmes, Zoe and Anders, Janet and Mintert, Florian}, title = {Enhanced energy transfer to an optomechanical piston from indistinguishable photons}, series = {Physical review letters}, volume = {124}, journal = {Physical review letters}, number = {21}, publisher = {American Physical Society}, address = {College Park, Md.}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.124.210601}, pages = {6}, year = {2020}, abstract = {Thought experiments involving gases and pistons, such as Maxwell's demon and Gibbs' mixing, are central to our understanding of thermodynamics. Here, we present a quantum thermodynamic thought experiment in which the energy transfer from two photonic gases to a piston membrane grows quadratically with the number of photons for indistinguishable gases, while it grows linearly for distinguishable gases. This signature of bosonic bunching may be observed in optomechanical experiments, highlighting the potential of these systems for the realization of thermodynamic thought experiments in the quantum realm.}, language = {en} } @article{AndersSaitHorsley2022, author = {Anders, Janet and Sait, Connor R. J. and Horsley, Simon A. R.}, title = {Quantum Brownian motion for magnets}, series = {New journal of physics : the open-access journal for physics}, volume = {24}, journal = {New journal of physics : the open-access journal for physics}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/ac4ef2}, pages = {21}, year = {2022}, abstract = {Spin precession in magnetic materials is commonly modelled with the classical phenomenological Landau-Lifshitz-Gilbert (LLG) equation. Based on a quantized three-dimensional spin + environment Hamiltonian, we here derive a spin operator equation of motion that describes precession and includes a general form of damping that consistently accounts for memory, coloured noise and quantum statistics. The LLG equation is recovered as its classical, Ohmic approximation. We further introduce resonant Lorentzian system-reservoir couplings that allow a systematic comparison of dynamics between Ohmic and non-Ohmic regimes. Finally, we simulate the full non-Markovian dynamics of a spin in the semi-classical limit. At low temperatures, our numerical results demonstrate a characteristic reduction and flattening of the steady state spin alignment with an external field, caused by the quantum statistics of the environment. The results provide a powerful framework to explore general three-dimensional dissipation in quantum thermodynamics.}, language = {en} } @article{RubioAndersCorrea2021, author = {Rubio, Jes{\´u}s and Anders, Janet and Correa, Luis A.}, title = {Global quantum thermometry}, series = {Physical review letters / publ. by the American Physical Society}, volume = {127}, journal = {Physical review letters / publ. by the American Physical Society}, number = {19}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.127.190402}, pages = {6}, year = {2021}, abstract = {A paradigm shift in quantum thermometry is proposed. To date, thermometry has relied on local estimation, which is useful to reduce statistical fluctuations once the temperature is very well known. In order to estimate temperatures in cases where few measurement data or no substantial prior knowledge are available, we build instead a method for global quantum thermometry. Based on scaling arguments, a mean logarithmic error is shown here to be the correct figure of merit for thermometry. Its full minimization provides an operational and optimal rule to postprocess measurements into a temperature reading, and it establishes a global precision limit. We apply these results to the simulated outcomes of measurements on a spin gas, finding that the local approach can lead to biased temperature estimates in cases where the global estimator converges to the true temperature. The global framework thus enables a reliable approach to data analysis in thermometry experiments.}, language = {en} }