Search results for "Quantum Mechanic"
showing 10 items of 2483 documents
Self-dressing in classical and quantum electrodynamics
2003
A short review is presented of the theory of dressed states in nonrelativistic QED, encompassing fully and partially dressed states in atomic physics. This leads to the concept of the reconstruction of the cloud of virtual photons and of self-dressing. Finally some recent results on the classical counterpart of self-dressing are discussed and a comparison is made with the QED case. Attention is drawn to open problems and future lines of research are briefly outlined.
Ultracold quantum gases in optical lattices
2005
Artificial crystals of light, consisting of hundreds of thousands of optical microtraps, are routinely created by interfering optical laser beams. These so-called optical lattices act as versatile potential landscapes to trap ultracold quantum gases of bosons and fermions. They form powerful model systems of quantum many-body systems in periodic potentials for probing nonlinear wave dynamics and strongly correlated quantum phases, building fundamental quantum gates or observing Fermi surfaces in periodic potentials. Optical lattices represent a fast-paced modern and interdisciplinary field of research.
Collective behavior ofMbosonic modes interacting with a single two-level atom
1988
The Hamiltonian describing, without the rotating-wave approximation (RWA), the linear interaction between M bosonic modes with an Einstein spectrum and a single two-level atom is exactly and canonically transformed introducing M suitable collective independent field modes, in such a way that only one among them is coupled to the atom. Some physical consequences of this fact are analyzed and, in particular, the existence of radiation-trapping phenomena together with the possibility of atomic absorption suppression is established. The applicability of the RWA to this system is discussed and the importance of the effective-field statistics for the time evolution of the system is pointed out.
Edwin Power and the birth of dressed atoms
2006
This paper reviews the main results of a twenty year-long international collaborative effort led by the late E.A. Power on the physics of atoms dressed by the vacuum electromagnetic field. The presentation uses the historical, rather than the logical, order of development. This permits one to shed light on the influence of Power's personality and human qualities on the birth and evolution of the notion of the dressed atom, which is central to modern non-relativistic QED.
Dynamics of a subconstituent picture of weak interactions
1985
We use sum rules in order to discuss the dynamics of the simplest subconstituent model of weak interactions with elementary spin 1/2 fermions and scalar bosons. Vacuum condensates of the scalars play an essential role and lead to features quite different from QCD. With a certain vacuum structure vector dominance of the composite W-mesons is a good approximation, and we also see a clear signal for massless fermions in the two-point function of composite fermions. Thus such a model is in good agreement with standard phenomenology. Composite Higgs particles are also investigated. The effective interaction is evidently of the gauge type.
Coherent and squeezed vibrations for discrete variable harmonic oscillators
2009
In this work we study different types of coherent and squeezed states for the Charlier, Kravchuk and Meixner oscillators. We calculate the average values of different observables corresponding to the coherent states. We found that the coherent and squeezed states of the Kravchuk oscillator are unstable. There are also coherent and squeezed states that are similar to the coherent and squeezed states of the harmonic oscillator. We have introduced a discrete variable model for the biophoton coherent radiation, and the coherent thermal and squeezed thermal states. © 2009 Taylor & Francis.
Simulating quantum-optical phenomena with optical lattices
2011
Cold atoms trapped in optical lattices have been proved to be very versatile quantum systems in which a large class of many-body condensed-matter Hamiltonians can be simulated [1].
Pairing in a three-component Fermi gas
2006
We consider pairing in a three-component gas of degenerate fermions. In particular, we solve the finite temperature mean-field theory of an interacting gas for a system where both interaction strengths and fermion masses can be unequal. At zero temperature we find a a possibility of a quantum phase transition between states associated with pairing between different pairs of fermions. On the other hand, finite temperature behavior of the three-component system reveals some qualitative differences from the two-component gas: for a range of parameters it is possible to have two different critical temperatures. The lower one corresponds to a transition between different pairing channels, while …
Dynamical mean-field theory versus second-order perturbation theory for the trapped two-dimensional Hubbard antiferromagnet
2011
In recent literature on trapped ultracold atomic gases, calculations for two-dimensional (2D) systems are often done within the dynamical mean-field theory (DMFT) approximation. In this paper, we compare DMFT to a fully 2D, self-consistent second-order perturbation theory for weak interactions in a repulsive Fermi-Hubbard model. We investigate the role of quantum and of spatial fluctuations when the system is in the antiferromagnetic phase, and find that, while quantum fluctuations decrease drastically the order parameter and critical temperatures, spatial fluctuations only play a noticeable role when the system undergoes a phase transition, or at phase boundaries in the trap. We conclude f…
Beyond the dilute Bose gas
2006
Abstract We discuss problems of three dimensional Bose gases in interaction but non-dilute. We then use the theory of a “weakly interacting” Bose gas recently analyzed as an attempt to obtain further insights into non-dilute systems. In particular, we develop the theory with additional remarks, discussions and a slight modification. The article concludes with a much more detailed analysis of the Bose condensate depletion, as well as a study of the two-fluid model of Tisza and Landau: the coexistence of normal and superfluid liquids at sufficiently low temperatures. In fact, even if it is based on one debatable hypothesis, this non-dilute gas qualitatively leads, up to Landau's “ T 4 law”, t…