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1

Transient Dynamics of Atoms Inside Submicron Rectangular Waveguides

100%

Al-Awfi S.

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EN

The time evolution of the radiation pressure forces due to the action of a laser light on two-level atom moving inside a long hollow cylinder with a rectangular cross-section of sub-wavelength dimensions a × b is presented. This evolution is considered when the frequency of the light is comparable to a dipole allowed transition frequency. In this limit, the decay emission Γp is possible only via a very small number of modes. From the solutions of the Bloch equations in the dynamic regime, we find that the transient regime, applicable from the instant the laser is switched on. This is important for the gross motion, provided that the upper-state lifetime Γp^{-1} is relatively long while the steady-state regime, formally such that t ≫ Γp^{-1}, is appropriate for the evaluation of the forces and the dynamics for large Γp. Significant variations of the characteristics of the system are emphasized. These features are illustrated using typical parameters for the case of Eu^{3+} that has a particularly small Γp.

2

Neutron Diffraction Studies of a Fully Asymmetric Diffraction Geometry of a Bent Perfect Crystal with the Output Beam Compression

100%

Mikula P., Vrána M., Šaroun J., Em V., Čapek J.

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EN

In this paper studies of neutron diffraction properties of the double crystal (+n,-m) setting of a bent perfect crystal Si(311) in the fully asymmetric diffraction geometry with the output beam compression and the bent perfect crystal Si(220) in a symmetric diffraction geometry, are presented. The properties of the (+n,-m) setting were studied for different curvatures of the individual crystal slabs. It has been found that after a beam condensation this fully asymmetric diffraction geometry can provide a monochromatic beam of a small width and of a practical use.

3

Control of Open Quantum Systems

80%

Japha Y., Kofman A., Kurizki G.

Acta Physica Polonica A

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1998

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vol. 93

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issue 1

135-145

EN

Spontaneous decay of excited cold atoms into a cavity can drastically affect their translational dynamics, namely, atomic reflection, transmission and localization at the interface. We show that the quantum Zeno effect on excitation decay of an atom is observable in open cavities and waveguides, using a sequence of evolution-interrupting pulses on a nanosecond scale.

4

On the Scattering of Neutron in the Magnetic Field οf 180° Bloch Wall

80%

Sazonov S.

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issue 3

449-453

EN

The exact solution of the Pauli equation has been derived for neutron wave propagating in magnetized continuum containing the magnetization non-uniformity such as the 180° Bloch wall, whose structure corresponds to the Landau-Lifshitz model. The scattering coefficients with and without neutron spin flip are presented as functions of ratio of neutron energy to the media's magnetic induction value. The possibility of narrow (≲100 Å) domain wall width measurement is discussed by the example of YFe_{11}Ti alloy.

5

Coherent Beam Splitting by a Thin Grating

70%

Božić M., Dimić D., Davidović M.

Acta Physica Polonica A

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2009

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vol. 116

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issue 4

479-482

EN

The wide use of beam splitters in quantum interferometry, attosecond metrology, modern quantum information processing, foundations of quantum mechanics, has been based on coherence of beams emerging from a beam splitter. Here we further develop the approach in which a beam splitter is regarded as a transformer of an incident wave field (photon field or matter wave field) into a field which has narrow maxima at the points along and in close vicinity of two or more particular lines. This description was derived by considering a thin grating as a model of a beam splitter for photons, atoms and molecules. It is applied to answer some questions raised in the discussions on the interpretation of wave particle duality.

6

Decoherence within a single atom

61%

Bene G.

Open Physics

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2003

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vol. 1

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issue 2

332-343

EN

An “almost diagonal” reduced density matrix (in coordinate representation) is usually a result of environment induced decherence and is considered the sign of classical behavior. We show that the proton of a ground state hydrogen atom can indeed possess such a density matrix. This example demonstrates that the “almost diagonal” structure may be derived from an interaction with a low number of degrees of freedom which play the role of the environment. We also show that decoherence effects in our example can only be observed if the interaction with the measuring device is significantly faster than the interaction with the environment (the electron). In the opposite case, when the interaction with the environment is significant during the measurement process, coherence is maintained. Finally, we propose a neutron scattering experiment on cold He atoms to observe decoherence which shows up as an additional positive contribution to the differential scattering cross section. This contribution is inversely proportional to the bombarding energy.

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