Topic
Coherence (physics)
About: Coherence (physics) is a research topic. Over the lifetime, 16631 publications have been published within this topic receiving 362434 citations. The topic is also known as: optical coherence & coherence of waves.
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01 May 1994
TL;DR: The annihilation operator for harmonic oscillator is a weighted shift operator and can be realized on a family of over complete coherent states, called harmonious states as discussed by the authors, which can be found in dynamical maps of systems exhibiting deterministic chaos.
Abstract: The annihilation operator for harmonic oscillator is a weighted shift operator and can be realized on a family of over complete coherent states. Shift operators arise in dynamical maps of systems exhibiting deterministic chaos. Generalized coherent states, called harmonious states, realize these maps in a simple manner. By analytic continuation the spectral family can be altered, thus furnishing an alternative perspective on resonant scattering. Singular distributions are necessary to reproduce the rich structure of chaotic and scattering systems.
3 citations
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28 Dec 1999
TL;DR: It was shown that the calculated coherent information is equal to zero for all types of the full measurement procedures, whereas it completely preserves its value for the quantum duplication procedure.
Abstract: The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information exchange between two coupled two-level atoms, and for the information transfer from a two-level atom to another atom and to a photon field. The coherent information is shown to be equal to zero for all full-measurement procedures, but it completely retains its original value for quantum duplication. Transmission of information from one open subsystem to another one in the entire closed system is analyzed to learn quantum information about the forbidden atomic transition via a dipole active transition of the same atom. It is argued that coherent information can be used effectively to quantify the information channels in physical systems where quantum coherence plays an important role.
3 citations
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24 Nov 2014
TL;DR: In this article, the coherence effects of wave propagation in disordered potentials is studied using ultracold atoms as a probe, a system allowing for a very good control over parameters such as the dimensionality, interactions, initial velocity of the atoms, and the potential landscape.
Abstract: In this manuscript the coherence effects of wave propagation in disordered potentials is studied. Our experiment uses ultracold atoms as a probe, a system allowing for a very good control over parameters such as the dimensionality, interactions, initial velocity of the atoms, and the potential landscape. Exploiting this flexibility we were able to perform experiments in the strongly and the weakly localized regime. In the former the 3D expansion of a BEC was monitored in real space, resulting in the observation of 3D Anderson localization with a maximum localized fraction of about 20%. In the latter the atoms were launched into a quasi-2D disorder with a well defined initial velocity. Monitoring the momentum space distribution the mean scattering time and the transport time can be directly measured, and coherent backscattering (CBS) is clearly visible as a peak in the backwards direction. In a first set of experiments the evolution of the CBS amplitude and width were recorded and found to be in good agreement with theory. Microscopically, CBS stems from the constructive interference of time-reversed multiply scattered paths. In a second set of CBS experiments we manipulated the time-reversal symmetry (TRS) of the wave propagation. A surgical dephasing was introduced via a shortly pulsed gradient field, which brakes TRS and suppresses CBS except for a brief moment, when a revival of CBS is observed. This novel effect showcases explicitly the role of coherence and TRS in Coherent Backscattering and weak localization.
3 citations
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TL;DR: In this article, the optical discontinuities located at domain walls in low-symmetry ferroelastics are responsible for the light-deflection phenomenon and for subsequent impairments of the intensity, the phase coherence, and the polarization of the direct beam transmitted through the domain structure.
Abstract: The optical discontinuities located at domain walls in low-symmetry ferroelastics are responsible for the light-deflection phenomenon and for subsequent impairments of the intensity, the phase coherence, and the polarization of the direct beam transmitted through the domain structure. Here, intensity losses are studied. Degradations of the coherence and the polarization are addressed in a companion paper. The deflected intensities are calculated as a function of the domain-wall density and of the average deformation of the polydomain sample. At first, a random phase hypothesis is assumed, then the calculation is refined by a two-wave interference model. Dichroic effects in deflection are predicted.
3 citations
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29 Mar 2012TL;DR: In this paper, the authors investigated the features of the CPT resonance on the D1 87 Rb line obtained in fluorescence in paraffin coated cells and found that the transformation from a black to a bright resonance is dependent on the laser power and the experimental geometry.
Abstract: The ultra-narrow resonances achieved in coherent spectroscopy of alkali atoms originate from the destruction of the laser-induced coherence in the ground state. An anti relaxation cell coating preserves the coherence created and, consequently, the resonance narrows by almost two orders of magnitude. Coherence resonances are used in magnetic field sensors, atomic clocks, quantum informatics, ets. In this work, we investigate the features of the CPT resonance on the D1 87 Rb line obtained in fluorescence in paraffin coated cells. The transformation from a black to a bright resonance is found to depend on the laser power and the experimental geometry.
3 citations