Decoherence induced by conical intersections: Complexity constrained quantum dynamics of photoexcited pyrazine

Abstract

Decoherence effects induced by conical intersecting potential energy surfaces are studied employing the correlation-based von Neumann (CvN) entropy which provides a measure of the complexity of the underlying wavefunction. As a prototypical example, the S(0) → S(2) excitation in pyrazine is investigated. The 24-dimensional wavepacket dynamics calculations presented utilize the multi-layer extension of the multi-configurational time-dependent Hartree (MCTDH) approach. An efficient numerical scheme is introduced which facilitates CvN entropy constrained wavepacket propagation within the multi-layer MCTDH approach. In unconstrained multi-layer MCTDH calculations, the CvN-entropy is found to provide a valuable analytical tool for studying the decoherence phenomena present. Investigating the CvN entropy after the S(0) → S(2) excitation as a function of time, a clear separation of time scales is obtained. It can be related to the different dynamical phenomena present: the initial transfer from the upper (S(2)) to the lower (S(1)) adiabatic electronic states rapidly generates vast amounts of CvN-entropy, while the subsequent motion on the anharmonic lower adiabatic potential energy surface only yields a slow increase of the CvN-entropy. Employing CvN-entropy constrained calculations, the sensitivity of the autocorrelation function, the absorption spectrum, and the diabatic electronic population dynamics to complexity constraints is analyzed in detail.

Fast Shepard interpolation on graphics processing units: Potential energy surfaces and dynamics for H + CH4 → H2 + CH3

“…It has been successfully applied to several high-dimensional systems. 41,72,[74][75][76][77][78][79][80][81][82][83][84][85] a) Electronic mail: rwelsch@uni-bielefeld.de b) Electronic mail: uwe.manthe@uni-bielefeld. de Recently the quantum transition state concept was extended to facilitate the calculation of state-to-state reaction probabilities 86,87 hopefully enabling detailed state-to-state calculations for H + CH 4 → H 2 + CH 3 .…”

Electron–vibration entanglement in the Born–Oppenheimer description of chemical reactions and spectroscopy

“…51 Another less explored reason for considering quantum entanglement within chemical systems is the possibility that it could provide new insight into the quantum world of molecular spectroscopy, thermodynamics, and kinetics, 50 and indeed this aspect is currently receiving significant attention. 6,30,31,[52][53][54] Previously we have investigated low-energy electron-vibration processes for use in quantum information processing, 2, 3 and here we extend this work to higher-energy processes. However, we are also concerned with what 55 entanglement can tell us about chemical reactions and spectroscopic processes, focusing not only the results that conceivable experiments may yield but also on the understanding of the breakdown of the Born-Oppenheimer (BO) and BornHuang (BH) adiabatic approximations.…”

“…However, owing to the fundamental importance of the BO approximation to the conceptual framework of chemistry, understanding this entanglement could yield conceptual advances. Indeed, this possibility is of considerable 70 current interest, 6,30,31,52,53 as is the possibility of examining vibration-vibration entanglement resulting from BO breakdown. 30,31 As classical molecular dynamics simulations based on the BO approximation do not allow for entanglement, the measures we provide may lead to a robust method for 75 accessing the suitability of molecular dynamics applications to chemical kinetics and spectroscopy.…”

“…The 35 entanglement is large in states that contain non-classical correlations, such as those seen in experiments in which Bell's inequalities are violated. In chemical applications, entanglement has been studied considering e.g., electron-vibration, [2][3][4][5][6][7][8][9][10][11][12][13][14][15] electronelectron, [16][17][18][19][20][21][22][23][24][25][26][27][28][29] vibration-vibration, [30][31][32][33][34][35][36][37][38][39][40][41] vibration-rotation, 42, 43 40 rotation-rotation, 44 and electron-spin [45][46][47][48][49] interactions. The primary motivation for this research has been the possibility of exploiting entanglement to fabricate a quantum information processing device with performance properties far in excess of those using classical electronics or optics.…”

Perspective: Nonadiabatic dynamics theory

“…58 A number of workers have introduced procedures for including decoherence, but there is still active discussion about this issue. [59][60][61][62][63][64][65][66] A third important concern with treating some degrees of freedom classically and others quantum mechanically is properly incorporating detailed balance. It is well known that a quantum system driven by a finite temperature classical system will eventually approach infinite temperature; energy passes artificially from the classical to the quantum subsystem.…”