Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userExtreme Parametric Sensitivity in the Steady-State Photoisomerization of Model Retinal
121
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The photoisomerization reaction of the retinal chromophore in rhodopsin was computationally studied using a two-state two-mode model coupled to thermal baths. Reaction quantum yields at the steady state (10 ps and beyond) were found to be considerably different than their transient values, suggesting a weak correlation between transient and steady-state dynamics in these systems. Significantly, the steady-state quantum yield was highly sensitive to minute changes in system parameters, while transient dynamics was nearly unaffected. Correlation of such sensitivity with standard level spacing statistics of the nonadiabatic vibronic system suggests a possible origin in quantum chaos. The feasibility of experimental observation of this phenomenon and its implications in condensed-phase photochemistry and biological light sensing are discussed.
rate research
Read More
We numerically study the implementation of a NOT gate by laser pulses in a model molecular system presenting two electronic surfaces coupled by non adiabatic interactions. The two states of the bit are the fundamental states of the cis-trans isomers of the molecule. The gate is classical in the sense that it involves a one-qubit flip so that the encoding of the outputs is based on population analysis which does not take the phases into account. This gate can also be viewed as a double photo-switch process with the property that the same electric field controls the two isomerizations. As an example, we consider one-dimensional cuts in a model of the retinal in rhodopsin already proposed in the literature. The laser pulses are computed by the Multi Target Optimal Control Theory with chirped pulses as trial fields. Very high fidelities are obtained. We also examine the stability of the control when the system is coupled to a bath of oscillators modelled by an Ohmic spectral density. The bath correlation time scale being smaller than the pulse duration the dynamics is carried out in the Markovian approximation.
All non-interacting two-dimensional electronic systems are expected to exhibit an insulating ground state. This conspicuous absence of the metallic phase has been challenged only in the case of low-disorder, low density, semiconducting systems where strong interactions dominate the electronic state. Unexpectedly, over the last two decades, there have been multiple reports on the observation of a state with metallic characteristics on a variety of thin-film superconductors. To date, no theoretical explanation has been able to fully capture the existence of such a state for the large variety of superconductors exhibiting it. Here we show that for two very different thin-film superconductors, amorphous indium-oxide and a single-crystal of 2H-NbSe2, this metallic state can be eliminated by filtering external radiation. Our results show that these superconducting films are extremely sensitive to external perturbations leading to the suppression of superconductivity and the appearance of temperature independent, metallic like, transport at low temperatures. We relate the extreme sensitivity to the theoretical observation that, in two-dimensions, superconductivity is only marginally stable.
The fitting of physical models is often done only using a single target observable. However, when multiple targets are considered, the fitting procedure becomes cumbersome, there being no easy way to quantify the robustness of the model for all different observables. Here, we illustrate that one can jointly search for the best model for each desired observable through multi-objective optimization. To do so we construct the Pareto front to study if there exists a set of parameters of the model that can jointly describe multiple, or all, observables. To alleviate the computational cost, the predicted error for each targeted objective is approximated with a Gaussian process model, as it is commonly done in the Bayesian optimization framework. We applied this methodology to improve three different models used in the simulation of stationary state $cis-trans$ photoisomerization of retinal in rhodopsin. Optimization was done with respect to different experimental measurements, including emission spectra, peak absorption frequencies for the $cis$ and $trans$ conformers, and the energy storage.
Alkaline-earth like atoms with ultra-narrow optical transitions enable superradiance in steady state. The emitted light promises to have an unprecedented stability with a linewidth as narrow as a few millihertz. In order to evaluate the potential usefulness of this light source as an ultrastable oscillator in clock and precision metrology applications it is crucial to understand the noise properties of this device. In this paper we present a detailed analysis of the intensity fluctuations by means of Monte-Carlo simulations and semi-classical approximations. We find that the light exhibits bunching below threshold, is to a good approximation coherent in the superradiant regime, and is chaotic above the second threshold.
A hybrid scheme is presented that allows the transfer of squeezed states (TSS) from the mechanical part to an optical cavity in the steady-state. In a standard optomechanical scheme, a three-level atom acts as an intermediate element for TSS. Two different procedures are developed that allow the visualization of the TSS effect: In the first one, we apply a coherent pump of squeezed phonons in our hybrid system, and the second method is achieved by placing the system in contact with a phonon squeezed bath. Our model and procedures show that in optomechanical systems TSS can be achieved with a high fidelity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
