Pseudomodes and the corresponding transformation of the temperature-dependent bath correlation function

In open system approaches with non-Markovian environments, the process of inserting an individual mode (denoted as "pseudomode") into the bath or extracting it from the bath is widely employed. This procedure, however, is typically performed on basis of the spectral density (SD) and does not incorporate temperature. Here, we show how the - temperature-dependent - bath correlation function (BCF) transforms in such a process. We present analytic formulae for the transformed BCF and numerically study the differences between factorizing initial state and global thermal (correlated) initial state of mode and bath, respectively. We find that in the regime of strong coupling of the mode to both system and bath, the differences in the BCFs give rise to pronounced differences in the dynamics of the system.Comment: 12 pages, 4 figure

Hierarchy of stochastic pure states for open quantum system dynamics

We derive a hierarchy of stochastic evolution equations for pure states (quantum trajectories) to efficiently solve open quantum system dynamics with non-Markovian structured environments. From this hierarchy of pure states (HOPS) the exact reduced density operator is obtained as an ensemble average. We demonstrate the power of HOPS by applying it to the Spin-Boson model, the calculation of absorption spectra of molecular aggregates and energy transfer in a photosynthetic pigment-protein complex

Conical intersections in an ultracold gas

We find that energy surfaces of more than two atoms or molecules interacting via dipole-dipole po- tentials generically possess conical intersections (CIs). Typically only few atoms participate strongly in such an intersection. For the fundamental case, a circular trimer, we show how the CI affects adiabatic excitation transport via electronic decoherence or geometric phase interference. These phe- nomena may be experimentally accessible if the trimer is realized by light alkali atoms in a ring trap, whose dipole-dipole interactions are induced by off-resonant dressing with Rydberg states. Such a setup promises a direct probe of the full many-body density dynamics near a conical intersection.Comment: 4 pages, 4 figures, replacement to add archive referenc

Non-Markovian Dynamics in Ultracold Rydberg Aggregates

We propose a setup of an open quantum system in which the environment can be tuned such that either Markovian or non-Markovian system dynamics can be achieved. The implementation uses ultracold Rydberg atoms, relying on their strong long-range interactions. Our suggestion extends the features available for quantum simulators of molecular systems employing Rydberg aggregates and presents a new test bench for fundamental studies of the classification of system-environment interactions and the resulting system dynamics in open quantum systems.Comment: 13 pages, 4 figure

Quantum simulation of energy transport with embedded Rydberg aggregates

We show that an array of ultracold Rydberg atoms embedded in a laser driven background gas can serve as an aggregate for simulating exciton dynamics and energy transport with a controlled environment. Spatial disorder and decoherence introduced by the interaction with the background gas atoms can be controlled by the laser parameters. This allows for an almost ideal realization of a Haken-Reineker-Strobl type model for energy transport. Physics can be monitored using the same mechanism that provides control over the environment. The degree of decoherence is traced back to information gained on the excitation location through the monitoring, turning the setup into an experimentally accessible model system for studying the effects of quantum measurements on the dynamics of a many-body quantum system.Comment: 5 pages, 4 figures, 3 pages supp. in

Optomechanical interactions in non-Hermitian photonic molecules

We study optomechanical interactions in non-Hermitian photonic molecules that support two photonic states and one acoustic mode. The nonlinear steady-state solutions and their linear stability landscapes are investigated as a function of the system\u27s parameters and excitation power levels. We also examine the temporal evolution of the system and uncover different regimes of nonlinear dynamics. Our analysis reveals several important results: (1) parity-time () symmetry is not necessarily the optimum choice for maximum optomechanical interaction. (2) Stable steady-state solutions are not always reached under continuous wave optical excitations. (3) Accounting for gain saturation effects can regulate the behavior of the otherwise unbounded oscillation amplitudes. Our study provides a deeper insight into the interplay between optical non-Hermiticity and optomechanical coupling and can thus pave the way for new device applications

Langzeitergebnisse nach CO₂-Laser-Tonsillotomie zur Behandlung schlafbezogener Atmungsstörungen im Kindesalter verglichen mit historischen Erfahrungen zur Tonsillotomie

Nach einem geschichtlichen Abriss der Tonsillotomie werden historische Arbeiten zur Erfassung entzündlicher Folgeerkrankungen nach Tonsillotomie vorgestellt. In eigenen Untersuchungen wurden retrospektiv 181 Patienten nach CO2-Laser-Tonsillotomie (Alter: 4,6 Jahre; SD ± 1,9) erfasst. 145 Patienten wurden über einen Beobachtungszeitraum von bis zu 6 Jahren (Mittelwert 3,0 Jahre) beurteilt. Es kam zu keiner Abszessbildung, bei weniger als 3% der Patienten wurden rezidivierende Tonsillitiden beobachtet. Versorgungspflichtige Nachblutungen traten bei lückenloser Erfassung nicht auf. Die obstruktive Symptomatik konnte auch langfristig signifikant vermindert oder aufgehoben werden. 95% der Eltern bewerteten den Gesamterfolg der Operation mit „gut“ oder „sehr gut“. Die CO2-Laser-Tonsillotomie stellt zur Behandlung der obstruktiven Tonsillenhyperplasie im Kleinkindesalter unter Beachtung einer entzündungsfreien Anamnese eine effektive und auch im Langzeitverlauf komplikationsarme Methode dar. First, an abstract of the history of the tonsillotomy is presented. Several historic papers on inflammatory secondary disorders following a tonsillotomy will be introduced. A total of 181 patients were observed following a tonsillotomy performed with CO2 laser (age: 4,6 years; std. dev. ± 1,9 years). 145 patients were evaluated over an observation period of up to 6 years (average 3,0 years). No abscess formation occurred, a re-occurrence of tonsillitis was observed in fewer than 3% of the patients. Subsequent bleeding requiring treatment did not occur during the post-operative progress. Obstructive symptoms could also be significantly reduced in the long-term. The overall success of the operation was evaluated by 95% of parents as “good” or “very good”. A CO2 laser tonsillotomy using for treatment of obstructive tonsil hyperplasy in small children (with consideration of an inflammation-free anamnesis) represents a safe, effective, and low-complication method, also for long-term continued development

Nanoelectromechanical rotary current rectifier

Nanoelectromechanical systems (NEMS) are devices integrating electrical and mechanical functionality on the nanoscale. Because of individual electron tunneling, such systems can show rich self-induced, highly non-linear dynamics. We show theoretically that rotor shuttles, fundamental NEMS without intrinsic frequencies, are able to rectify an oscillatory bias voltage over a wide range of external parameters in a highly controlled manner, even if subject to the stochastic nature of electron tunneling and thermal noise. Supplemented by a simple analytic model, we identify different operational modes of charge rectification. Intriguingly, the direction of the current depends sensitively on the external parameters

Coherently delocalized states in dipole interacting Rydberg ensembles: the role of internal degeneracies

We investigate the effect of degenerate atomic states on the exciton delocalization of dipole-dipole interacting Rydberg assemblies. Using a frozen gas and regular one-, two-, and three-dimensional lattice arrangements as examples, we see that degeneracies can enhance the delocalization compared to the situation when there is no degeneracy. Using the Zeeman splitting provided by a magnetic field, we controllably lift the degeneracy to study in detail the transition between degenerate and non-degenerate regimes

Topological edge states in a Rydberg composite

We examine topological phases and symmetry-protected electronic edge states in the context of a Rydberg composite: a Rydberg atom interfaced with a structured arrangement of ground-state atoms. The electronic Hamiltonian of such a composite possesses a direct mapping to a tight-binding Hamiltonian, which enables the realization and study of a variety of systems with non-trivial topology by tuning the arrangement of ground-state atoms and the excitation of the Rydberg atom. The Rydberg electron moves in a combined potential including the long-ranged Coulomb interaction with the Rydberg core and short-ranged interactions with each neutral atom; the effective interactions between sites are determined by this combination. We first confirm the existence of topologically-protected edge states in a Rydberg composite by mapping it to the paradigmatic Su-Schrieffer-Heeger dimer model. Following that, we study more complicated systems with trimer unit cells which can be easily simulated with a Rydberg composite.Comment: 5 pages, 4 figure