Initial State Dependence Research Articles

Robust Effective Ground State in a Nonintegrable Floquet Quantum Circuit.

An external periodic (Floquet) drive is believed to bring any initial state to the featureless infinite temperature state in generic nonintegrable isolated quantum many-body systems in the thermodynamic limit, irrespective of the driving frequency Ω. However, numerical or analytical evidence either proving or disproving this hypothesis is very limited and the issue has remained unsettled. Here, we study the initial state dependence of Floquet heating in a nonintegrable kicked Ising chain of length up to L=30 with an efficient quantum circuit simulator, showing a possible counterexample: the ground state of the effective Floquet Hamiltonian is exceptionally robust against heating, and could stay at finite energy density even after infinitely many Floquet cycles, if the driving period is shorter than a threshold value. This sharp energy localization transition or crossover does not happen for generic excited states. The exceptional robustness of the ground state is interpreted by (i)its isolation in the energy spectrum and (ii)the fact that those states with L-independent ℏΩ energy above the ground state energy of any generic local Hamiltonian, like the approximate Floquet Hamiltonian, are atypical and viewed as a collection of noninteracting quasiparticles. Our finding paves the way for engineering Floquet protocols with finite driving periods realizing long-lived, or possibly even perpetual, Floquet phases by initial state design.

Path-dependence of the Plio–Pleistocene glacial/interglacial cycles

We find strong path dependence in the evolution of the Plio-Pleistocene glaciations using CLIMBER-2 Earth System Model simulations from the mid-Pliocene to modern preindustrial (3 My-0 My BP) driven by a gradual decrease in volcanic carbon dioxide outgassing and regolith removal from basal ice interaction. Path dependence and hysteresis are investigated by alternatively driving the model forward and backward in time. Initiating the model with preindustrial conditions and driving the model backward using time-reversed forcings, the increase in volcanic outgassing back-in-time (BIT) does not generate the high CO2 levels and relatively ice-free conditions of the late Pliocene seen in forward-in-time (FIT) simulations of the same model. This behavior appears to originate from nonlinearities and initial state dependence in the carbon cycle. A transition from low-amplitude sinusoidal obliquity (~41 ky) and precession (~23 ky) driven glacial/interglacial cycles to high-amplitude ~100 ky likely eccentricity-related sawtooth cycles seen between -1.25 My and -0.75 My BP (the Mid-Pleistocene transition or "MPT") in FIT simulations disappears in BIT integrations depending on the details of how the regolith removal process is treated. A transition toward depleted regolith and lowered atmospheric CO2 levels are both required to reproduce the MPT.

Quantum Dynamics of O(3P)+HBr→OH+Br Reaction: Integral Cross Sections and Rate Constants and their Initial State Dependence.

The integral cross sections (ICSs) and rate constants (RCs) for the title reaction are calculated by means of accurate quantum wave packet method employing the recent ab initio potential energy surface developed by Peterson and co-workers. Hundreds of partial wave contributions (up to J=150) are calculated explicitly taking Coriolis coupling into account. The ICSs are found to increase monotonically with energy and their energy dependences are smooth except in the energy range below the potential energy barrier, where several resonance peaks are observed. The temperature dependences of the RCs obey in general the Arrhenius law. These behaviors manifest the dominance of abstract mechanism. Initial rotational state (ji) excitations are found to greatly enhance the reactivity starting from ji=4, while exhibiting a complicated dependence for ji<4. From Boltzmann average of the initial state specified RCs (for ji=0-15) we obtained thermal RCs which are in reasonable agreement with available experimental results.

Advances in exploration of photoinduced electron transfer reactions involving small molecules probed by magnetic field effect

The review focuses on photoinduced electron transfer (PET) reactions between small molecules and various kinds of chemical and biological systems using a weak external magnetic field (MF). Laser flash photolysis is a competent tool to characterize the intermediates which are formed due to PET. A weak MF, very close to the hyperfine interaction of the system, has the potential to inhibit or enhance reaction channels for singlet and triplet states, which eventually effects the product distribution. At first, well-documented examples of PET involving small molecules like derivatives of phenazines, carbazoles and acridines with classical electron donors in varying homogeneous and heterogeneous media have been discussed and the influence of a weak MF on the dynamics of PET is highlighted. Secondly, utilization of magnetic field effect (MFE) to probe PET in protein pockets has been described. Thirdly, an extensive discussion on PET involving nucleobases, nucleosides, nucleotides and nucleic acids and subsequent MFE on such reactions has been reported. Next, MFE has been exploited to study PET involving nanomaterials. Finally, some very recent studies of MFE have been discussed. Thus, this review is an attempt to unravel various aspects of PET in a large number of systems of varying dimensions by means of several facets of MFE like B1/2 parameter, its capability to authenticate the initial spin state and distance dependence property.

Pretrial predictors of conflict response efficacy in the human prefrontal cortex

The ability to perform motor actions depends, in part, on the brain's initial state. We hypothesized that initial state dependence is a more general principle and applies to cognitive control. To test this idea, we examined human single units recorded from the dorsolateral prefrontal (dlPFC) cortex and dorsal anterior cingulate cortex (dACC) during a task that interleaves motor and perceptual conflict trials, the multisource interference task (MSIT). In both brain regions, variability in pre-trial firing rates predicted subsequent reaction time (RT) on conflict trials. In dlPFC, ensemble firing rate patterns suggested the existence of domain-specific initial states, while in dACC, firing patterns were more consistent with a domain-general initial state. The deployment of shared and independent factors that we observe for conflict resolution may allow for flexible and fast responses mediated by cognitive initial states. These results also support hypotheses that place dACC hierarchically earlier than dlPFC in proactive control.

Interplay of many-body interactions and quasiperiodic disorder in the all-bands-flat diamond chain

We study the effects of quasiperiodic Aubry-Andr\'e (AA) disorder and interactions on a one-dimensional all-band-flat (ABF) diamond chain. We consider the application of disorder in two ways: a symmetric one, where the same disorder is applied to the top and bottom sites of a unit cell, and an antisymmetric one, where the disorder applied to the top and bottom sites are of equal magnitude but with opposite signs. The single-particle wave-packet dynamics for the clean system and when the disorder is applied symmetrically show quantum caging; in the antisymmetric case, the wave-packet spreads over the entire lattice. These results agree with our previous work, where compact localization was observed in the case of the clean system and for symmetrically disordered diamond lattices. In the presence of nearest-neighbour interactions, nonergodic phases are observed in the case of a clean system and symmetrical disorder; at higher disorder strengths, we find an MBL-like phase in the symmetric case. However, many-body non-equilibrium dynamics of the system from carefully engineered initial states exhibit quantum caging. In the antisymmetric case, a nonergodic mixed phase, a thermal phase and an MBL-like phases, respectively, are observed at low, intermediate and high disorder strengths. We observe an absence of caging and initial state dependence (except at the intermediate disorder strength) in the study of non-equilibrium dynamics.

Initial-state dependence of phase behaviors in a dense active system

There are rich emergent phase behaviors in non-equilibrium active systems. Flocking and clustering are two representative dynamic phases. The relationship between both the phases is still unclear. Herein, we numerically investigate the evolution of flocking and clustering in a system consisting of self-propelled particles with active reorientation. We consider the interplay between flocking and clustering phases with different initial configurations, and observe a domain in steady state order parameter phase diagrams sensitive to the choice of initial configurations. Specifically, by tuning the initial degree of polar ordering, either a more ordered flocking or a disordered clustering state can be observed in the steady state. These results enlighten us to manipulate emergent behaviors and collective motions of an active system, and are qualitatively different from the emergence of a new bi-stable regime observed in aligned active particles due to an explicit attraction [New J. Phys. 14 073033 (2012)].

Scrambling and entangling spinning particles

In this paper we revisit the gravitational eikonal amplitudes of two scattering spinning particles and inspect their scrambling power in the spin spaces that is quantified through the tripartite information. We found that in the non-relativistic limit and a special high-energy limit the leading contribution is a quantity that is universal and theory independent. The minimal coupling is singled out with minimal scrambling in a different high momenta limit. We also inspected the initial state dependence of entanglement generation and found that the spin coherent state with vanishing spin may not necessarily be the hardest to entangle. Interestingly, among a family of mixed states, the only P-rep state there known to be the best approximation of classical mixed states was singled out as one with minimal entanglement generated.

Emergence of Hilbert Space Fragmentation in Ising Models with a Weak Transverse Field.

The transverse-field Ising model is one of the fundamental models in quantum many-body systems, yet a full understanding of its dynamics remains elusive in higher than one dimension. Here, we show for the first time the breakdown of ergodicity in d-dimensional Ising models with a weak transverse field in a prethermal regime. We demonstrate that novel Hilbert-space fragmentation occurs in the effective nonintegrable model with d≥2 as a consequence of only one emergent global conservation law of the domain wall number. Our results indicate nontrivial initial-state dependence for nonequilibrium dynamics of the Ising models with a weak transverse field.

Impossibility of achieving Landauer's bound for almost every quantum state

The thermodynamic cost of resetting an arbitrary initial state to a particular desired state is lower bounded by Landauer's bound. However, here we demonstrate that this lower bound is necessarily unachievable for every initial state (except possibly the single minimally dissipative input) for any reliable reset mechanism. Since local heating threatens rapid decoherence, this issue is of substantial importance beyond mere energy efficiency. For the case of qubit reset, we find the minimally dissipative state analytically for any reliable reset protocol, in terms of the entropy-flow vector introduced here. This allows us to verify a recent theorem about initial-state dependence of entropy production for any finite-time transformation, as it pertains to quantum state preparation.

Parameter identification of fractional-order time delay system based on Legendre wavelet

This paper proposes a parameter identification method of fractional-order time delay system based on Legendre wavelet. An integration operational matrix and delay operational matrix of a Legendre wavelet are constructed. The process is derived to convert a fractional-order time delay system based on a Legendre wavelet operational matrix to algebraic equation. The least squares method is used to simultaneously estimate the order, model parameters and time delay coefficient of a system. In addition, wavelet decomposition and reconstruction algorithm are used to pre-process the output signal, which separate the noise from signal. The proposed method overcomes the initial-state dependence and randomness of the identification result in the algebraic solution of the traditional operational matrix, and reduces the effect of noise on the accuracy of parameter identification. It is especially suitable for engineering application. The effectiveness is verified by numerical simulation and a temperature process control system.

Initial-state dependence of thermodynamic dissipation for any quantum process.

Exact results about the nonequilibrium thermodynamics of open quantum systems at arbitrary timescales are obtained by considering all possible variations of initial conditions of a system. First we obtain a quantum-information theoretic equality for entropy production, valid for an arbitrary initial joint state of system and environment. For any finite-time process with a fixed initial environment, we then show that the system's loss of distinction-relative to the minimally dissipative state-exactly quantifies its thermodynamic dissipation. The quantum component of this dissipation is the change in coherence relative to the minimally dissipative state. Implications for quantum state preparation and local control are explored. For nonunitary processes-like the preparation of any particular quantum state-we find that mismatched expectations lead to divergent dissipation as the actual initial state becomes orthogonal to the anticipated one.

Photoionization of open-shell nitrogen confined in C60

Endofullerene photoionization of open-shell N@C60 is investigated using a coupled-channel, correlated R-matrix approach with additional modifications for a finite spherical-shell fullerene potential. Particular focus is on the initial-state dependence of the photoionization cross section. Comparisons show significant differences between the 1s 22s 22p 3(4S) initial state and the metastable 2D and 2P states, as well as strong confinement oscillations.

Initial state dependence in the configuration optimization of a point-like scatters lens

Initial state dependence in the configuration optimization of a point-like scatters lens

Photoionization of the open-shell nitrogen atom confined in C60

SynopsisEndofullerene photoionization of open-shell N@C60 is investigated using a coupled-channel, correlated R-matrix approach with additional modifications for a finite spherical-shell fullerene potential. Particular focus is on the initial-state dependence of the photoionization cross section. Comparisons show significant differences between the 1s 22s 22p 3(4S) initial state and the metastable 2D and 2P states, as well as strong confinement oscillatory structure.

Probing charge transfer dynamics in a single iron tetraphenylporphyrin dyad adsorbed on an insulating surface.

Although the dynamics of charge transfer (CT) processes can be probed with ultimate lifetime resolution, the inability to control CT at the nanoscale is one of the most important roadblocks to revealing some of its deep fundamental aspects. In this work, we present an investigation of CT dynamics in a single iron tetraphenylporphyrin (Fe-TPP) donor/acceptor dyad adsorbed on a CaF2/Si(100) insulating surface. The tip of a scanning tunneling microscope (STM) is used to create local ionic states in one fragment of the dyad. The CT process is monitored by imaging subsequent changes in the neighbor acceptor molecule and its efficiency is mapped, revealing the influence of the initial excited state in the donor molecule. In the validation of the experiments, simulations based on density functional theory show that holes have a higher donor-acceptor CT rate compared to electrons and highlight a noticeable initial state dependence on the CT process. We leverage the unprecedented spatial resolution achieved in our experiments to show that the CT process in the dyad is governed via molecule-molecule coherent tunneling with negligible surface-mediated character.

An Effect of Mass Transport and Pt Oxide Formation on High Current Density Performance in PEFC

Introduction High current density operation is essential to cost reduction of polymer electrolyte fuel cell (PEFC) system for automotive application. Although extensive numerical1,2) and experimental3,4) approaches have been conducted in order to understand and to predict a cell performance under high current density condition, there was no comprehensive analysis with microscopic transport resistance on Pt surface, catalyst activity change associate with Pt oxide formation, water and heat transport. In this study, polarization curves under high current density were validated with quantification of both proper catalyst activity and mass transport effects. Obtained results suggested that catalyst activity with oxide formation is important for deeper understanding of over-potential under high current density condition. Experimental and Numerical Modeling Polarization curves were evaluated under extremely low oxygen concentration (0.4%) and normal condition (10%) in order to validate the effect of heat, water and proton transport respectively. Supplied gases were controlled at 200 kPa (Abs.) with high enough flow rate into low pressure drop straight flow channel to minimize oxygen and reaction distribution along flow direction. To evaluate the initial state dependence of adsorbed species on Pt surface, scanning rate of potential was controlled very low (0.5 mV· sec-1) from low potential (0.3 V) to high potential (1.0 V) region. Pt loadings of test cell were 0.35 mg· cm-2 and 0.10 mg· cm-2to evaluate the effect of both mass transport resistance and activity change in catalyst associate with effective Pt surface area. In the numerical analysis model, continuous equations, momentum, conservation formula of chemical species, and potential (electronic and electrolyte) formulas were combined, and the source and sink term associated with electrochemical reaction was given by the Butler Volmer equation. Transport characteristic values were measured by the evaluation method described in previous reports 1,2) . Oxide formation on platinum surface was considered the active site change assuming Langmuir adsorption and adsorption energy change exerted by adsorbed species covering the site in the vicinity assuming Temkin adsorption3,4), coupled analysis of electrochemical reactions and three-dimensional mass transport corresponding to activity changes due to potential changes. In addition, the oxide coverage ratio was experimentally approximated by the CV test. The numerical model also made it possible to simplify to one-dimensional analysis for studying three-dimensional mass transport effect on polarization curves. Results and Discussions Fig.1 shows results of experiment (dashed line) and numerical validation (solid line) with/without considering effect of Pt oxide formation and three-dimensional mass transport. One-dimensional models analysis indicated that Pt oxide formation doesn’t have effects on limiting current density but has effects on over-potential nonlinearly from the region below 0.75 V. It was roughly in agreement that oxide species on catalyst surface almost all desorbed based on the CV test result in previous report3) and indicates that electrochemical reaction characteristics in low potential regions is also important for cell performance analysis. Furthermore, regarding the comparison of one-dimensional model and three-dimensional model considering Pt oxide, even if thin rib (0.2 mm) configuration is used under extremely low oxygen concentration operation, over-potential under high current density increased due to influences of three dimensional mass transport, electrochemical reaction distribution. Conclusion In this study, polarization curves under high current density condition were validated by the numerical analysis with both proper catalyst activity and three-dimensional mass transport effects. Validation results suggested over-potential under high current density operation is strongly affected by not only three-dimensional mass transport but also Pt oxide formation associated with potential change as well. Reference [1] Y. Tabuchi et al. / Electrochimica Acta., 56, 352 (2010) [2] Y. Fukuyama et al. / Electrochimica Acta., 117, 367 (2014) [3] S. Sugawara et al. / J. Eletrochemisty., 79, 404 (2011) [4] N.M. Marković et al. / J. Eletroanal. Chem., 467, 157 (1999) Figure 1

Initial-state dependence of the route to chaos of an external-cavity laser

External-cavity semiconductor lasers (ECLs), consisting of a laser diode in front of a mirror to reflect light back into the laser diode, are among the most important dynamical systems because of their ultrafast dynamics, their tunability, and the numerous existing applications. The dynamics of an ECL is greatly influenced by the existence and stability of numerous modes of the external cavity. In such high-dimensional nonlinear systems, numerous attractors, located around various modes of the external cavity, can coexist in phase space for a given set of parameters, a phenomenon called generalized multistability. In this work, we propose a procedure that allows one to select experimentally different modes of the external cavity as different initial states. We use this procedure to reveal experimentally generalized multistability in an ECL through the demonstration that different routes to chaos exist in an ECL, depending on the initial state selected. In particular, we show that the famous quasiperiodic route to chaos is only observed for specific choices of initial conditions.

Initial-state dependence of a quantum resonance ratchet

We demonstrate quantum resonance ratchets created with Bose-Einstein condensates exposed to pulses of an off-resonant standing light wave. We show how some of the basic properties of the ratchets are controllable through the creation of different initial states of the system. In particular, our results prove that through an appropriate choice of initial state it is possible to reduce the extent to which the ratchet state changes with respect to time. We develop a simple theory to explain our results and indicate how ratchets might be used as part of a matter wave interferometer or quantum-random walk experiment.

Regional and gender differentials in the persistence of unemployment in Europe

The persistence of unemployment increased during the recent great recession in many European countries, although with diversified impacts. We therefore analyse such impacts in four European countries – Italy, Spain, France and the UK – which represent different institutional frameworks and may reflect the so-called continental European and Anglo-Saxon frameworks. We analyse the determinants of unemployment persistence using individual-level data from the European Union Statistics on Income and Living Conditions (EU-SILC) panel for the period 2007–2013. These data enable us to take into account initial conditions and state dependence in addition to individual and household characteristics. We focus on gender and regional effects, which have a strong impact on the persistence in the state of unemployment. We find that gender gap is significant in Italy and the UK, implying that male workers show a higher probability of remaining unemployed. In Italy, such a pattern is due to the worsening of male workers’ conditions during the crisis, whereas in the UK, male workers show higher unemployment rates than women. Regional effects are significant in all countries analysed and underline a relevant structural factor that should be addressed on policy grounds in Europe. Such effects are greater in Spain and Italy.