arXiv subjects

Ivan P. Christov

Publications and source records attributed to Ivan P. Christov.

23 records · Page 2Linked to original sources

arXiv2013

Electron-pair densities with time-dependent quantum Monte-Carlo

In this paper we use sets of de Broglie-Bohm trajectories to describe the quantum correlation effects which take place between the electrons in helium atom due to exchange and Coulomb interactions. A short-range screening of the Coulomb potential is used to modify the repulsion between the same spin electrons in physical space in order to comply with the Pauli's exclusion principle. By calculating the electron-pair density for ortho-helium we found that the shape of the exchange hole can be controlled uniquely by a simple screening parameter. For para-helium the inter-electronic distance, and hence the Coulomb hole, results from the combined action of the Coulomb repulsion and the non-local quantum correlations. In this way a robust and self-interaction-free approach is presented to find both the ground state and the time evolution of non-relativistic quantum systems.

physics.atom-ph↗

arXiv2012

Exploring quantum non-locality with de Broglie-Bohm trajectories

Here in this paper, it is shown how the quantum nonlocality reshapes probability distributions of quantum trajectories in configuration space. By variationally minimizing the ground state energy of helium atom we show that there exists an optimal nonlocal quantum correlation length which also minimizes the mean integrated square error of the smooth trajectory ensemble with respect to the exact many-body wave function. The nonlocal quantum correlation length can be used for studies of both static and driven many-body quantum systems.

quant-ph↗

arXiv2007

Time-dependent quantum Monte Carlo and the stochastic quantization

We examine the relation between the recently proposed time-dependent quantum Monte Carlo (TDQMC) method and the principles of stochastic quantization. In both TDQMC and stochastic quantization particle motion obeys stochastic guidance equations to preserve quantum equilibrium. In this way the probability density of the Monte Carlo particles corresponds to the modulus square of the many-body wave function at all times. However, in TDQMC the motion of particles and guide waves occurs in physical space unlike in stochastic quantization where it occurs in configuration space. Hence the practical calculation of time evolution of many-body fully correlated quantum systems becomes feasible within the TDQMC methodology. We illustrate the TDQMC technique by calculating the symmetric and antisymmetric ground state of a model one-dimensional Helium atom, and the time evolution of the dipole moment when the atom is irradiated by a strong ultrashort laser pulse.

physics.atom-ph↗

arXiv2006

Quantum trajectory perspective of atom-field interaction in attosecond time scale

Here the ionization and high harmonic generation in Hydrogen and Helium by using quantum (hydrodynamic) trajectories is analyzed theoretically. The quantum trajectories allow a self-contained treatment of the electron exchange and correlation effects without introducing ad hoc potentials into the Schrodinger equation. Our approach predicts the correct high harmonic spectra and the attosecond pulses generated by the Helium atom beyond the single active electron approximation. It can be used to study complex multi-electron systems and their interaction with laser field of both high and low intensity.

physics.atom-ph↗

arXiv2006

Correlated non-perturbative electron dynamics with quantum trajectories

An approach to electron correlation effects in atoms that uses quantum trajectories is presented. A comparison with the exact quantum mechanical results for 1D Helium atom shows that the major features of the correlated ground state distribution and of the strong field ionization dynamics are reproduced with quantum trajectories. The intra-atomic resonant transitions are described accurately by a trajectory ensemble. The present approach reduces significantly the computational time and it can be used for both bound and ionizing electrons.

physics.atom-ph↗