Search results for "Quantum Mechanics"

Nonlocal properties of entangled two-photon generalized binomial states in two separate cavities

2007

We consider entangled two-photon generalized binomial states of the electromagnetic field in two separate cavities. The nonlocal properties of this entangled field state are analyzed by studying the electric field correlations between the two cavities. A Bell's inequality violation is obtained using an appropriate dichotomic cavity operator, that is in principle measurable.

Tuning the collective decay of two entangled emitters by means of a nearby surface

2017

We consider the radiative properties of a system of two identical correlated atoms interacting with the electromagnetic field in its vacuum state in the presence of a generic dielectric environment. We suppose that the two emitters are prepared in a symmetric or antisymmetric superposition of one ground state and one excited state and we evaluate the transition rate to the collective ground state, showing distinctive cooperative radiative features. Using a macroscopic quantum electrodynamics approach to describe the electromagnetic field, we first obtain an analytical expression for the decay rate of the two entangled two-level atoms in terms of the Green's tensor of the generic external en…

Berry's phase in Cavity QED: proposal for observing an effect of field quantization

2002

Geometric phases are well known in classical electromagnetism and quantum mechanics since the early works of Pantcharatnam and Berry. Their origin relies on the geometric nature of state spaces and has been studied in many different systems such as spins, polarized light and atomic physics. Recent works have explored their application in interferometry and quantum computation. Earlier works suggest how to observe these phases in single quantum systems adiabatically driven by external classical devices or sources, where, by classical, we mean any system whose state does not change considerably during the interaction time: an intense magnetic field interacting with a spin 1/2, or a birefringe…

New Quantum Effects in the Dynamics of a Two-mode Field Coupled to a Two-level Atom

1994

Abstract The dynamics of a degenerate two-mode electromagnetic field coupled to a single two-level atom is investigated both analytically and numerically. New quantum effects are discussed concerning the time dependence of the photon number and of its fluctuations, assuming that at t = 0 one of the modes is coherent and the other is empty. The field dynamics are dominated by oscillatory net exchanges of a large number of photons between the two modes, displaying amplitude decay. Over a longer time scale, revivals and collapses in the field populations take place. The time scales of these phenomena are much larger than those of the atomic Rabi oscillations decay. Moreover, the system attains…

Reply to “Comment on ‘Limits of the measurability of the local quantum electromagnetic field amplitude’ ”

1999

Time-dependent Maxwell field operators and field energy density for an atom near a conducting wall

2009

We consider the time evolution of the electric and magnetic field operators for a two-level atom, interacting with the electromagnetic field, placed near an infinite perfectly conducting wall. We solve iteratively the Heisenberg equations for the field operators and obtain the electric and magnetic energy density operators around the atom (valid for any initial state). Then we explicitly evaluate them for an initial state with the atom in its bare ground state and the field in the vacuum state. We show that the results can be physically interpreted as the superposition of the fields propagating directly from the atom and the fields reflected on the wall. Relativistic causality in the field …

The renormalized electron mass in non-relativistic quantum electrodynamics

2007

This work addresses the problem of infrared mass renormalization for a scalar electron in a translation-invariant model of non-relativistic QED. We assume that the interaction of the electron with the quantized electromagnetic field comprises a fixed ultraviolet regularization and an infrared regularization parametrized by $\sigma>0$. For the value $p=0$ of the conserved total momentum of electron and photon field, bounds on the renormalized mass are established which are uniform in $\sigma\to0$, and the existence of a ground state is proved. For $|p|>0$ sufficiently small, bounds on the renormalized mass are derived for any fixed $\sigma>0$. A key ingredient of our proofs is the operator-t…

Exact solution of generalized Tavis - Cummings models in quantum optics

1996

Quantum inverse methods are developed for the exact solution of models which describe N two-level atoms interacting with one mode of the quantized electromagnetic field containing an arbitrary number of excitations M. Either a Kerr-type nonlinearity or a Stark-shift term can be included in the model, and it is shown that these two cases can be mapped from one to the other. The method of solution provides a general framework within which many related problems can similarly be solved. Explicit formulae are given for the Rabi splitting of the models for some N and M, on- and off-resonance. It is also shown that the solution of the pure Tavis - Cummings model can be reduced to solving a homogen…

Inter- and intramolecular bonding in 1,3,5-triamino-2,4,6-trinitrobenzene: An experimental and theoretical quantum theory of atoms in molecules (QTAI…

2017

Chemical bonding in the triclinic phase of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been analyzed based on the experimental electron density derived from X-ray diffraction data obtained at 20 K. The results have been compared with those from solid state theoretical calculations. The total electron density has been analyzed in terms of the Quantum Theory of Atoms in Molecules (QTAIM). Features of the covalent bonds demonstrate the presence of multiple bonds of various order. Strong intramolecular hydrogen bonds and weaker intermolecular bonds within the layer structure are characterized by the properties of their (3, −1) critical points. Weaker interactions, predominantly O···O, betwe…

Hybrid QM/MM Molecular Dynamics with AMOEBA Polarizable Embedding

2017

International audience; We present the implementation of a Born-Oppenheimer (BO) hybrid Quantum Mechan-ics/Molecular Mechanics (QM/MM) Molecular Dynamics (MD) strategy using Density Functional Theory (DFT) and the polarizable AMOEBA force field. This approach couples the Gaussian and Tinker suite of programs through a variational formalism allowing for a full self-consistent relaxation of both the AMOEBA induced dipoles and the DFT electronic density at each MD step. As the DFT SCF cycles are the limiting factor in terms of computational efforts and MD stability, we focus on the latter aspect and compare the Time-Reversible BO (TR– BO) and the Extended BO Lagrangian approaches (XL–BO) to th…