Simulating Non-Markovian Dynamics in Multidimensional Electronic Spectroscopy via Quantum Algorithm.

Including the effect of the molecular environment in the numerical modeling of time-resolved electronic spectroscopy remains an important challenge in computational spectroscopy. In this contribution, we present a general approach for the simulation of the optical response of multichromophore systems in a structured environment and its implementation as a quantum algorithm. A key step of the procedure is the pseudomode embedding of the system-environment problem resulting in a finite set of quantum states evolving according to a Markovian quantum master equation.

A Quantum Algorithm from Response Theory: Digital Quantum Simulation of Two-Dimensional Electronic Spectroscopy.

Multidimensional optical spectroscopies are powerful techniques to investigate energy transfer pathways in natural and artificial systems. Because of the high information content of the spectra, numerical simulations of the optical response are of primary importance to assist the interpretation of spectral features. However, the increasing complexity of the investigated systems and their quantum dynamics call for the development of novel simulation strategies.

Nonlinear Optical Spectroscopy of Molecular Assemblies: What Is Gained and Lost in Action Detection?

This study elucidates the information content that is extracted from action-2D electronic spectroscopy (A-2DES) when the output intensity is not proportional to the number of excitations generated. Such a scenario can be realized in both fluorescence and photocurrent detection because of interaction like exciton-exciton annihilation or effects in the signal generation or detection. By means of an intuitive probabilistic model supported by nonlinear response theory, the study concludes that in molecular assemblies the ground-state bleaching contribution can dominate the nonlinear signal and partially or completely hide the stimulated emission.

Identification of Design Principles for the Preparation of Colloidal Plexcitonic Materials.

Colloidal plexcitonic materials (CPMs) are a class of nanosystems where molecular dyes are strongly coupled with colloidal plasmonic nanoparticles, acting as nanocavities that enhance the light field. As a result of this strong coupling, new hybrid states are formed, called plexcitons, belonging to the broader family of polaritons. With respect to other families of polaritonic materials, CPMs are cheap and easy to prepare through wet chemistry methodologies.

Unifying Nonlinear Response and Incoherent Mixing in Action-2D Electronic Spectroscopy.

Action-detection has expanded the scope and applicability of 2D electronic spectroscopy, while posing new challenges for the unambiguous interpretation of spectral features. In this context, identifying the origin of cross-peaks at early waiting times is not trivial, and incoherent mixing is often invoked as an unwanted contribution masking the nonlinear signal. In this work, we elaborate on the relation between the nonlinear response and the incoherent mixing contribution by analyzing the action signal in terms of one- and two-particle observables.

Large barrier behavior of the rate constant from the diffusion equation.

Many processes in chemistry, physics, and biology depend on thermally activated events in which the system changes its state by surmounting an activation barrier. Examples range from chemical reactions to protein folding and nucleation events. Parameterized forms of the mean field potential are often employed in the stochastic modeling of activated processes.

Simulating action-2D electronic spectroscopy of quantum dots: insights on the exciton and biexciton interplay from detection-mode and time-gating.

Action-2D electronic spectroscopy is emerging as a powerful technique to investigate exciton dynamics in molecular aggregates and nanostructures. While maintaining the power of highlighting coherent evolution between the laser pulses, action detection is based on measuring the incoherent signal proportional to the excited-state populations generated by an additional laser pulse. Numerical simulations of the action signal play a crucial role in aiding the interpretation of the spectral features, which may differ from those of the analog coherent technique in a non-trivial way.

Spectral shift, electronic coupling and exciton delocalization in nanocrystal dimers: insights from all-atom electronic structure computations.

Delocalization of excitons promoted by electronic coupling between clusters or quantum dots (QD) changes the dynamical processes in nanostructured aggregates enhancing energy transport. A spectroscopic shift of the absorption spectrum upon QD aggregation is commonly observed and ascribed to quantum mechanical coupling between neighbouring dots but also to exciton delocalization over the sulphur-based ligand shell or to other mechanisms as a change in the dielectric constant of the surrounding medium. We address the question of electronic coupling and exciton delocalization in nanocrystal aggregates by performing all-atom electronic structure calculations in models of colloidal QD dimers.

Stability of antibacterial Te(IV) compounds: A combined experimental and computational study.

Inorganic Te(IV) compounds are important cysteine protease inhibitors and antimicrobial agents; AS-101 [ammonium trichloro (dioxoethylene-O,O')tellurate] is the first compound of a family with formula NH[CHClOTe], where a Te(IV) centre is bound to a chelate ethylene glycol, and showed several protective therapeutic applications. This compound is lacking in stability performance and is subjected to hydrolysis reaction with displacement of the diol ligand. In this paper, we report the stability trend of a series of analogues complexes of AS-101 with generic formula NH[(RCHO)ClTe], where R is an alkyl group with different chain length and different electronic properties, in order to find a correlation between structure and stability in aqueous-physiological conditions.

Thermal Pure States for Finite and Isolated Quantum Systems.

We study an ensemble of quantum pure states, the thermalization resilient ensemble (TRE), providing the statistical characterization of the thermal equilibrium of isolated quantum systems. Following a previous work where the ensemble was defined based on the invariance of the average populations upon thermal contact of identical systems, here we introduce a general methodology to generate quantum states according to the TRE statistic. The sampling is employed to characterize the ensemble distribution of thermodynamic functions like the entropy, internal energy, and temperature.

Implementation of Multivariable Logic Functions in Parallel by Electrically Addressing a Molecule of Three Dopants in Silicon.

To realize low-power, compact logic circuits, one can explore parallel operation on single nanoscale devices. An added incentive is to use multivalued (as distinct from Boolean) logic. Here, we theoretically demonstrate that the computation of all the possible outputs of a multivariate, multivalued logic function can be implemented in parallel by electrical addressing of a molecule made up of three interacting dopant atoms embedded in Si.

Implementation of Probabilistic Algorithms by Multi-chromophoric Molecular Networks with Application to Multiple Travelling Pathways.

The implementation of probabilistic algorithms by deterministic hardware is demanding and requires hundreds of instructions to generate a pseudo-random sequence of numbers. On the contrary, the dynamics at the molecular scale is physically governed by probabilistic laws because of the stochastic nature of thermally activated and quantum processes. By simulating the exciton transfer dynamics in a multi-chromophoric system, we demonstrate the implementation of a random walk that samples the possible pathways of a traveler through a network and can be probed by time-resolved fluorescence spectroscopy.

A Probabilistic Finite State Logic Machine Realized Experimentally on a Single Dopant Atom.

Exploiting the potential of nanoscale devices for logic processing requires the implementation of computing functionalities departing from the conventional switching paradigm. We report on the design and the experimental realization of a probabilistic finite state machine in a single phosphorus donor atom placed in a silicon matrix electrically addressed and probed by scanning tunneling spectroscopy (STS). The single atom logic unit simulates the flow of visitors in a maze whose topology is determined by the dynamics of the electronic transport through the states of the dopant.

Force measurements reveal how small binders perturb the dissociation mechanisms of DNA duplex sequences.

The force-driven separation of double-stranded DNA is crucial to the accomplishment of cellular processes like genome transactions. Ligands binding to short DNA sequences can have a local stabilizing or destabilizing effect and thus severely affect these processes. Although the design of ligands that bind to specific sequences is a field of intense research with promising biomedical applications, so far, their effect on the force-induced strand separation has remained elusive.

Quantum Statistical Ensemble Resilient to Thermalization.

The sampling of the wave function within a suitable ensemble is an important tool in the statistical analysis of a molecule interacting with its environment. The uniform statistical distribution of quantum pure states in an active space is often the privileged choice. However, such a distribution with constant average populations of eigenstates is not preserved upon the interaction between quantum systems.

Information processing in parallel through directionally resolved molecular polarization components in coherent multidimensional spectroscopy.

We propose that information processing can be implemented by measuring the directional components of the macroscopic polarization of an ensemble of molecules subject to a sequence of laser pulses. We describe the logic operation theoretically and demonstrate it by simulations. The measurement of integrated stimulated emission in different phase matching spatial directions provides a logic decomposition of a function that is the discrete analog of an integral transform.

Parallel and Multivalued Logic by the Two-Dimensional Photon-Echo Response of a Rhodamine−DNA Complex.

Implementing parallel and multivalued logic operations at the molecular scale has the potential to improve the miniaturization and efficiency of a new generation of nanoscale computing devices. Two-dimensional photon-echo spectroscopy is capable of resolving dynamical pathways on electronic and vibrational molecular states. We experimentally demonstrate the implementation of molecular decision trees, logic operations where all possible values of inputs are processed in parallel and the outputs are read simultaneously, by probing the laser-induced dynamics of populations and coherences in a rhodamine dye mounted on a short DNA duplex.

Atomistic account of structural and dynamical changes induced by small binders in the double helix of a short DNA.

Nucleic acids are flexible molecules and their dynamical properties play a key role in molecular recognition events. Small binders interacting with DNA fragments induce both structural and dynamical changes in the double helix. We study the dynamics of a DNA dodecamer and of its complexes with Hoechst 33258, which is a minor groove binder, and with the ethidium cation, which is an intercalator, by molecular dynamics simulation.

Molecular decision trees realized by ultrafast electronic spectroscopy.

The outcome of a light-matter interaction depends on both the state of matter and the state of light. It is thus a natural setting for implementing bilinear classical logic. A description of the state of a time-varying system requires measuring an (ideally complete) set of time-dependent observables.

Beyond quantum microcanonical statistics.

Descriptions of molecular systems usually refer to two distinct theoretical frameworks. On the one hand the quantum pure state, i.e.

Emergence of equilibrium thermodynamic properties in quantum pure states. II. Analysis of a spin model system.

A system composed of identical spins and described by a quantum mechanical pure state is analyzed within the statistical framework presented in Part I of this work. We explicitly derive the typical values of the entropy, of the energy, and of the equilibrium reduced density matrix of a subsystem for the two different statistics introduced in Part I. In order to analyze their consistency with thermodynamics, these quantities of interest are evaluated in the limit of large number of components of the isolated system.

Emergence of equilibrium thermodynamic properties in quantum pure states. I. Theory.

Investigation on foundational aspects of quantum statistical mechanics recently entered a renaissance period due to novel intuitions from quantum information theory and to increasing attention on the dynamical aspects of single quantum systems. In the present contribution a simple but effective theoretical framework is introduced to clarify the connections between a purely mechanical description and the thermodynamic characterization of the equilibrium state of an isolated quantum system. A salient feature of our approach is the very transparent distinction between the statistical aspects and the dynamical aspects in the description of isolated quantum systems.

Typicality in ensembles of quantum states: Monte Carlo sampling versus analytical approximations.

Random quantum states are presently of interest in the fields of quantum information theory and quantum chaos. Moreover, a detailed study of their properties can shed light on some foundational issues of the quantum statistical mechanics such as the emergence of well-defined thermal properties from the pure quantum mechanical description of large many-body systems. When dealing with an ensemble of pure quantum states, two questions naturally arise, what is the probability density function on the parameters which specify the state of the system in a given ensemble, and does there exist a "most typical" value of a function of interest in the considered ensemble? Here, two different ensembles are considered, the random pure state ensemble (RPSE) and the fixed expectation energy ensemble (FEEE).

Collective fluctuations in ordered fluids investigated by two-dimensional electron-electron double resonance spectroscopy.

Two-dimensional electron-electron double resonance (2D-ELDOR) is a technique that is sensitive to the dynamical processes affecting spin labels in complex fluid environments. In ordered fluids, such as membrane vesicles, the 2D-ELDOR experiment is affected by the molecular tumbling in the locally ordered environment. This motion occurs on two different time scales, the faster molecular motion relative to the local director, and the slower collective fluctuations of the director field.