Engineering vibrationally-assisted energy transfer in a trapped-ion quantum simulator

Many important chemical and biochemical processes in the condensed phase are notoriously difficult to simulate numerically. Often this difficulty arises from the complexity of simulating dynamics resulting from coupling to structured, mesoscopic baths, for which no separation of time scales exists and statistical treatments fail. A prime example of such a process is vibrationally assisted charge or energy transfer. A quantum simulator, capable of implementing a realistic model of the system of interest, could provide insight into these processes in regimes where numerical treatments fail. We take a first step towards modeling such transfer processes using an ion trap quantum simulator. By implementing a minimal model, we observe vibrationally assisted energy transport between the electronic states of a donor and an acceptor ion augmented by coupling the donor ion to its vibration. We tune our simulator into several parameter regimes and, in particular, investigate the transfer dynamics in the nonperturbative regime often found in biochemical situations

Gas-phase diagnostics by laser-induced gratings II. Experiments

In this article we review the results achieved in the past ten years at the Paul Scherrer Institute on the topic of diagnostics in the gas phase by laser-induced gratings (LIGs). The technique has been applied for thermometry in air and in flames at different pressures, for flow velocimetry, for concentration measurements, and for imaging purposes. The influence of collisional energy-transfer and relaxation processes in molecules on the temporal evolution of the LIG signals has also been investigated. It has been demonstrated that, for molecules with a low fluorescence quantum yield, excitation of laser-induced thermal gratings can be used as a sensitive spectroscopic tool. For the quantitative interpretation of the experiments shown in this work, the findings presented in the companion paper [1] have been use

Gas phase diagnostics by laser-induced gratings I. theory

Electrostriction and collisional thermalization of absorbed laser energy are the two dominant mechanisms leading to the formation of laser-induced gratings (LIGs) in the gas phase. In this article the results of the theoretical investigations that have been achieved in the past ten years at the Paul Scherrer Institute on this issue are summarized and yield a comprehensive understanding of the underlying physical concepts. Furthermore, a study of the influence of various parameters, such as the alignment and the spatial intensity profile of the beams on the generated electrostrictive and thermal signal is presented for the first time to the authors' knowledge. The variations of the refractive index responsible for the appearance of laser-induced gratings have been theoretically described by solving the linearized hydrodynamic equations. The contributions from electrostriction, as well as from instantaneous and slow relaxation of the absorbed radiation energy into heat is obtained. These expressions are employed for analysis of experimental data presented in the companion paper [1] which is devoted to the application of the technique for diagnostic purposes in the gas phase. Much effort has been undertaken in order to allow a straightforward physical interpretation of the experimental findings of the expressions presented her

Injection locking of a low cost high power laser diode at 461 nm

Stable laser sources at 461 nm are important for optical cooling of strontium atoms. In most existing experiments this wavelength is obtained by frequency doubling infrared lasers, since blue laser diodes either have low power or large emission bandwidths. Here, we show that injecting less than 10 mW of monomode laser radiation into a blue multimode 500 mW high power laser diode is capable of slaving at least 50% of the power to the desired frequency. We verify the emission bandwidth reduction by saturation spectroscopy on a strontium gas cell and by direct beating of the slave with the master laser. We also demonstrate that the laser can efficiently be used within the Zeeman slower for optical cooling of a strontium atomic beam.Comment: 2nd corrected version (minor revisions); Manuscript accepted for publication in Review of Scientific Instruments; 5 pages, 6 figure

Noise Thermometry with Two Weakly Coupled Bose-Einstein Condensates

Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.Comment: 4 pages, 4 figure

Residential green space and air pollution are associated with brain activation in a social-stress paradigm

We examined the influence of three major environmental variables at the place of residence as potential moderating variables for neurofunctional activation during a social-stress paradigm. Data from functional magnetic resonance imaging of 42 male participants were linked to publicly accessible governmental databases providing information on amount of green space, air pollution, and noise pollution. We hypothesized that stress-related brain activation in regions important for emotion regulation were associated positively with green space and associated negatively with air pollution and noise pollution. A higher percentage of green space was associated with stronger parietal and insular activation during stress compared with that in the control condition. More air pollution was associated with weaker activation in the same (but also extended) brain regions. These findings may serve as an important reference for future studies in the emerging field of “neuro-urbanism” and emphasize the importance of environmental factors in urban planning

Realization of a single Josephson junction for Bose-Einstein condensates

We report on the realization of a double-well potential for Rubidium-87 Bose-Einstein condensates. The experimental setup allows the investigation of two different dynamical phenomena known for this system - Josephson oscillations and self-trapping. We give a detailed discussion of the experimental setup and the methods used for calibrating the relevant parameters. We compare our experimental findings with the predictions of an extended two-mode model and find quantitative agreement