Search results for "Adiabatic theorem"
showing 10 items of 30 documents
A consistent microscopic theory of collective motion in the framework of an ATDHF approach
1978
Based on merely two assumptions, namely the existence of a collective Hamiltonian and that the collective motion evolves along Slater determinants, we first derive a set of adiabatic time-dependent Hartree-Fock equations (ATDHF) which determine the collective path, the mass and the potential, second give a unique procedure for quantizing the resulting classical collective Hamiltonian, and third explain how to use the collective wavefunctions, which are eigenstates of the quantized Hamiltonian.
Many-Body Quantum Dynamics from the Density
2013
We present a local control scheme to construct the external potential v that, for a given initial state, produces a prescribed time-dependent density in an interacting quantum many-body system. This numerical method is efficient and stable even for large and rapid density variations irrespective of the initial state and the interactions. It can at the same time be used to answer fundamental v-representability questions in density functional theory. In particular, in the absence of interactions, it allows us to construct the exact time-dependent Kohn-Sham potential for arbitrary initial states. We illustrate the method in a correlated one-dimensional two-electron system with different intera…
Decoherence-free creation of atom-atom entanglement in cavity via fractional adiabatic passage
2005
We propose a robust and decoherence insensitive scheme to generate controllable entangled states of two three-level atoms interacting with an optical cavity and a laser beam. Losses due to atomic spontaneous transitions and to cavity decay are efficiently suppressed by employing fractional adiabatic passage and appropriately designed atom-field couplings. In this scheme the two atoms traverse the cavity-mode and the laser beam in opposite directions as opposed to other entanglement schemes in which the atoms are required to have fixed locations inside a cavity. We also show that the coherence of a traveling atom can be transferred to the other one without populating the cavity-mode.
A pseudo-Jahn–Teller model of the photochromic effect in sodium nitroprusside
2003
Abstract A new model for the photochromic effect in sodium nitroprusside Na2[Fe(CN)5(NO)]·2H2O based on the concept of the pseudo-Jahn–Teller effect is proposed. The model takes into account the electron transfer from the Fe2+ ion to the π* orbitals of the NO-ligand as well as the vibronic mixing of three electronic states of the Fe NO fragment through the non-symmetric and full-symmetric modes. The problem is solved within the adiabatic approximation. Under certain conditions the lower sheet of the adiabatic potential is shown to possess three minima with the increasing energies that correspond to the N-bound, sideways bound and O-bound NO group. The barriers between the minima are estimat…
Mixed-Valence Molecular Unit for Quantum Cellular Automata: Beyond the Born-Oppenheimer Paradigm through the Symmetry-Assisted Vibronic Approach.
2016
In this article, we focus on the electron-vibrational problem of the tetrameric mixed-valence (MV) complexes proposed for implementation as four-dot molecular quantum cellular automata (mQCA).1 Although the adiabatic approximation explored in ref 2 is an appropriate tool for the qualitative analysis of the basic characteristics of mQCA, like vibronic trapping of the electrons encoding binary information and cell-cell response, it loses its accuracy providing moderate vibronic coupling and fails in the description of the discrete pattern of the vibronic levels. Therefore, a precise solution of the quantum-mechanical vibronic problem is of primary importance for the evaluation of the shapes o…
Analytic estimation of transition between instantaneous eigenstates of quantum two-level system
2018
AbstractTransition amplitudes between instantaneous eigenstates of a quantum two-level system are evaluated analytically on the basis of a new parametrization of its evolution operator, which has recently been proposed to construct exact solutions. In particular, the condition under which the transitions are suppressed is examined analytically. It is shown that the analytic expression of the transition amplitude enables us, not only to confirm the adiabatic theorem, but also to derive the necessary and sufficient condition for quantum two-level system to remain in one of the instantaneous eigenstates.
Oscillator Strengths of Electronic Excitations with Response Theory using Phase Including Natural Orbital Functionals
2013
The key characteristics of electronic excitations of many-electron systems, the excitation energies ωα and the oscillator strengths fα, can be obtained from linear response theory. In one-electron models and within the adiabatic approximation, the zeros of the inverse response matrix, which occur at the excitation energies, can be obtained from a simple diagonalization. Particular cases are the eigenvalue equations of time-dependent density functional theory (TDDFT), time-dependent density matrix functional theory, and the recently developed phase-including natural orbital (PINO) functional theory. In this paper, an expression for the oscillator strengths fα of the electronic excitations is…
Quantum effects in the capture of charged particles by dipolar polarizable symmetric top molecules. I. General axially nonadiabatic channel treatment
2013
The rate coefficients for capture of charged particles by dipolar polarizable symmetric top molecules in the quantum collision regime are calculated within an axially nonadiabatic channel approach. It uses the adiabatic approximation with respect to rotational transitions of the target within first-order charge-dipole interaction and takes into account the gyroscopic effect that decouples the intrinsic angular momentum from the collision axis. The results are valid for a wide range of collision energies (from single-wave capture to the classical limit) and dipole moments (from the Vogt-Wannier and fly-wheel to the adiabatic channel limit).
Pseudo-Jahn–Teller Origin of the Metastable States in Sodium Nitroprusside
2003
Abstract A new model for the photochromic effect in sodium nitroprusside Na 2 [Fe(CN) 5 (NO)]·2H 2 O based on the concept of the pseudo-Jahn–Teller effect is proposed. The model takes into account the electron transfer from the Fe 2+ ion to the π ∗ orbitals of the NO-ligand as well as the vibronic mixing of three electronic states of the Fe–NO fragment through the non-symmetric and full symmetric modes. The problem is solved within the adiabatic approximation. Under certain conditions, the lower sheet of the adiabatic potential is shown to possess three minima with the increasing energies that correspond to the N-bound, sideways bound, and O-bound NO group. The barriers between the minima a…
Spheroidal and hyperspheroidal coordinates in the adiabatic representation of scattering states for the Coulomb three-body problem
2009
Recently, an involved approach has been used by Abramov (2008 J. Phys. B: At. Mol. Opt. Phys. 41 175201) to introduce a separable adiabatic basis into the hyperradial adiabatic (HA) approximation. The aim was to combine the separability of the Born–Oppenheimer (BO) adiabatic basis and the better asymptotic properties of the HA approach. Generalizing these results we present here three more different separable bases of the same type by making use of a previously introduced adiabatic Hamiltonian expressed in hyperspheroidal coordinates (Matveenko 1983 Phys. Lett. B 129 11). In addition, we propose a robust procedure which accounts in a stepwise procedure for the unphysical couplings that are …