Search results for " ELECTRODYNAMICS"

The physical origin of a photon-number parity effect in cavity quantum electrodynamics

2021

Abstract The rapidly increasing capability to modulate the physicochemical properties of atomic groups and molecules by means of their coupling to radiation, as well as the revolutionary potential of quantum computing for materials simulation and prediction, fuel the interest for non-classical phenomena produced by atom-radiation interaction in confined space. One of such phenomena is a “parity effect” that arises in the dynamics of an atom coupled to two degenerate cavity field modes by two-photon processes and manifests itself as a strong dependence of the field dynamics on the parity of the initial number of photons. Here we identify the physical origin of this effect in the quantum corr…

Resonant atom-field interaction in large-size coupled-cavity arrays

2011

We consider an array of coupled cavities with staggered inter-cavity couplings, where each cavity mode interacts with an atom. In contrast to large-size arrays with uniform-hopping rates where the atomic dynamics is known to be frozen in the strong-hopping regime, we show that resonant atom-field dynamics with significant energy exchange can occur in the case of staggered hopping rates even in the thermodynamic limit. This effect arises from the joint emergence of an energy gap in the free photonic dispersion relation and a discrete frequency at the gap's center. The latter corresponds to a bound normal mode stemming solely from the finiteness of the array length. Depending on which cavity …

Fast Control of Quantum States in Quantum Dots: Limits due to Decoherence

2005

We study the kinetics of confined carrier-phonon system in a quantum dot under fast optical driving and discuss the resulting limitations to fast coherent control over the quantum state in such systems.

Erratum: Atom-field dressed states in slow-light waveguide QED [Phys. Rev. A93, 033833 (2016)]

2016

We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multiphoton dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide both a qualitative and quantitative description of the essential strong-…

Time-resolved observation of coherent multi-body interactions in quantum phase revivals

2010

Interactions between microscopic particles are usually described as two-body interactions, although it has been shown that higher order multi-body interactions could give rise to novel quantum phases with intriguing properties. This paper demonstrates effective six-body interactions in a system of ultracold bosonic atoms in a three-dimensional optical lattice. The coherent multi-particle interactions observed here open a new window for simulations of effective field theories and may help to enable the realization of novel topologically ordered many-body quantum phases. Interactions between microscopic particles are usually described as two-body interactions, although it has been shown that …

Feel the force

2014

An approach based on quantum sensing, in which controlled quantum systems serve as precision sensors, has enabled measurement of the weak magnetic interaction between two electrons bound to two separate ions. See Letter p.376 Every electron carries an intrinsic magnetic dipole moment, so any two electrons should therefore exert magnetic forces on one another. The forces involved are very small, and at atomic scale Coulomb interaction is dominant, so it is extremely difficult to observe the magnetic interaction. However, Shlomi Kotler et al. have now done just that, measuring the interaction between two electrons, in separate trapped strontium-88 ions. The two electrons exhibit spin entangle…

Quantum Computing Experiments with Cold Trapped Ions

2016

Two-loop calculation of the anomalous dimension of the axial current with static heavy quarks

1992

Abstract A method to perform two-loop calculations in Eichten's effective field theory for heavy quarks is developed. The anomalous dimension of the axial current for static heavy quarks is calculated at two loops. For N = 3, we get γ A (2) = − 1 36 [ 127 2 +28ξ(2)−5N f ] . This result is very important to understand completely the physical significance of the lattice measurement of the decay constant of the B meson. The two-loop correction generated by γ A (2) turns out to be small, less than 1% for four quark flavours, so that the value of the decay constant of the B meson does not need in practice renormalization group improvement. As extra results, the self-energy renormalization consta…

Antiscreening of the Ampère force in QED and QCD plasmas

2013

The static forces between electric charges and currents are modified at the loop level by the presence of a plasma. While electric charges are screened, currents are not. The effective coupling constant at long distances is enhanced in both cases as compared to the vacuum, and by different amounts, a clear sign that Lorentz symmetry is broken. We investigate these effects quantitatively, first in a QED plasma and secondly using non-perturbative simulations of QCD with two light degenerate flavors of quarks.

Minimally doubled fermions at one loop

2009

Minimally doubled fermions have been proposed as a cost-effective realization of chiral symmetry at non-zero lattice spacing. Using lattice perturbation theory at one loop, we study their renormalization properties. Specifically, we investigate the consequences of the breaking of hyper-cubic symmetry, which is a typical feature of this class of fermionic discretizations. Our results for the quark self-energy indicate that the four-momentum undergoes a renormalization which contains a linearly divergent piece. We also compute renormalization factors for quark bilinears, construct the conserved vector and axial-vector currents and verify that at one loop the renormalization factors of the lat…