Quantum dynamics and control of vibrational dephasing

Abstract

This review emphasizes the physical principles underlying the dephasing of nonstationary vibrational states of molecules with multiple vibrational degrees of freedom. The motion of atoms within molecules can be described to a very good approximation by a many-level system of coupled anharmonic quantized oscillators. The separation of electronic and nuclear timescales, combined with weak symmetry breaking inherent in molecular structures, guarantees that the Hamiltonian can always be cast in a form that is local in the quantum state space of the molecular vibrations. The resulting nonexponential dephasing dynamics can be controlled with external fields to stabilize nonstationary quantum states, and both quantum–classical and fully quantum control formalisms are described. Coupled molecular vibrations interacting with external fields also offer prospects for quantum computing because vibrational level spacings can be made very large compared to thermal noise, and relaxation mechanisms such as infrared fluorescence are many orders of magnitude slower than the timescales required for coherence transfer. Finally, a toy model that provides insights into the interaction of vibrational degrees of freedom with ‘solvent’ modes is also discussed, and exhibits nonexponential dynamics in certain regimes.

Ab initio study of exciton transfer dynamics from a core–shell semiconductor quantum dot to a porphyrin-sensitizer

“…The pathway taken by the photoexcitation in the QD-dye nanoassembly is best described with the modern theory of energy transfer, which is greatly motivated by search for novel energy sources, design of artificial light-harvesting systems, and understanding the efficient light harvesting seen in nature [32][33][34][35][36][37][38]. The energy and electron transfer processes in the light-harvesting systems are driven by the ultrafast photoinduced evolution of the electronic degrees of freedom, which are strongly affected by the dynamic reorganization of the quantized vibrational modes [39][40][41]. Therefore, theoretical description of the transfer processes requires explicit modeling of the coupled electronic and vibrational dynamics together with bath-induced dephasing and renormalization of the system energies [40][41][42][43][44][45].…”

Dynamical tunnelling in molecules: quantum routes to energy flow

“…The state |a is not symmetrically located, refering to the arguments following Eq. (38), with respect to |b and thus, combined with the smallness of λ mi1 , does not show significant mixing. Given that the key resonances and their strengths are known (cf.…”

“…The review [33] by Nesbitt and Field gives an excellent introduction to the literature. The review [38] by Gruebele highlights the recent advances and the possibility of controlling IVR. The topic of molecular energy flow in solutions has been recently reviewed [39] by Aßmann, Kling and Abel.…”

Probing coherence aspects of adiabatic quantum computation and control

“…Quite a bit of effort has gone into the study of pure states of multilevel systems for recent developments in coherent control [28][29][30][31] and for quantum computing. 9,11,32 However, there has been almost no effort to explore the dynamics as one deviates from the pure-state picture though there have been previous attempts that utilized the dressed state formalism.…”