Search results for "electromagnetic"

Bose-Einstein Condensation in an electro-pneumatically transformed quadrupole-Ioffe magnetic trap

2014

We report a novel approach for preparing a Bose-Einstein condensate (BEC) of $^{87}$Rb atoms using electro-pneumatically driven transfer of atoms into a Quadrupole-Ioffe magnetic trap (QUIC Trap). More than 5$\times$$10^{8}$ atoms from a Magneto-optical trap are loaded into a spherical quadrupole trap and then these atoms are transferred into an Ioffe trap by moving the Ioffe coil towards the center of the quadrupole coil, thereby, changing the distance between quadrupole trap center and the Ioffe coil. The transfer efficiency is more than 80 \%. This approach is different from a conventional approach of loading the atoms into a QUIC trap wherein the spherical quadrupole trap is transformed…

Effect of the electromagnetic environment on arrays of small normal metal tunnel junctions: Numerical and experimental investigation

2000

We present results of a set of experiments to investigate the effect of dissipative external electromagnetic environment on tunneling in linear arrays of junctions in the weak tunneling regime. The influence of this resistance decreases as the number of junctions in the chain increases and ultimately becomes negligible. Further, there is a value of external impedance, typically \~5 k$\Omega$, at which the half-width of the zero-voltage dip in the conductance curve shows a maximum. Some new analytical formulae, based on the phase-correlation theory, along with numerical results will be presented.

Feasibility of Coulomb blockade thermometry in metrology

2000

Abstract Coulomb blockade thermometer (CBT) is a simple, magnetic-field-independent primary thermometer for everyday use at cryogenic temperatures. Its properties are well understood by now. The absolute accuracy at present is about ±0.5%. Recently, we have started studying the possibility of using CBT in metrological applications. We have especially in mind the future extension of the international temperature scale below 0.65 K, which is the lower end of ITS-90. Experiments with arrays containing more than 100 tunnel junctions in series are in progress in order to decrease the effects of electromagnetic environment and of co-tunnelling even below the present level.

On the anomalous Stark effect in a thin disc-shaped quantum dot

2010

The effect of a lateral external electric field F on an exciton ground state in an InAs disc-shaped quantum dot has been studied using a variational method within the effective mass approximation. We consider that the radial dimension of the disc is very large compared to its height. This situation leads to separating the excitonic Hamiltonian into two independent parts: the lateral confinement which corresponds to a two-dimensional harmonic oscillator and an infinite square well in the growth direction. Our calculations show that the complete description of the lateral Stark shift requires both the linear and quadratic terms in F which explains that the exciton possess nonzero lateral dipo…

Magnetostrictive and quadrupolar anisotropy in nuclear magnetic fcc systems

1992

The spin hamiltonian for nuclear magnetic order in copper is investigated with respect to magnetoelastic couplings to the lattice. These arise due to the dipolar, Ruderman Kittel and the quadrupolar interaction. While the latter is quenched for the ideal fcc-lattice, it is found that for copper it will dominate the magnetoelastic terms of the nuclear spin hamiltonian. The absolute size of the quadrupole contribution is determined by the effective charge and (anti-) shielding effects. This interaction can give rise to an effective anisotropy in the fcc-system which can be quite large compared to the small stabilisation energies for nuclear order in copper. Consequences for the nuclear orderi…

Slowing down of light pulses using backward-wave four-wave mixing with local response

2015

The slowing down of light pulses is achieved using backward-wave four-wave mixing in a medium with local response. A Bi12TiO20 crystal with an external dc field is used in the experiment as a proof-of-concept material. The delay and shape transformation of output pulses are studied and compared for the transmitted and phase conjugate channels. It is shown that the phase conjugate pulse achieves a longer delay under typical experimental conditions with equal intensities of the pump beams. This advantage of the phase conjugate beam is especially pronounced for short pulses with half-widths smaller than the response time of the medium. The agreement of the experimental results with numerical c…

Microwave heating as a tool for coupling Marangoni and Hickman instabilities

2007

The aim of this paper is the linear stability analysis of an evaporating interface in order to justify hydrodynamic behaviors observed during evaporation of water and ethanol simultaneously under microwave irradiation and reduced pressure. In relation to the local character of the thermal conversion of electromagnetic energy, and of the thermal dependency of the dielectric loss, it seems possible under microwave heating to induce a specific hydrodynamic compared to those induced by conventional heating.

form factor at order of chiral perturbation theory

2001

Abstract This paper describes the calculation of the electromagnetic form factor of the K 0 meson at order p 6 of chiral perturbation theory which is the next-to-leading order correction to the well-known p 4 result achieved by Gasser and Leutwyler. On the one hand, at order p 6 the chiral expansion contains 1- and 2-loop diagrams which are discussed in detail. Especially, a numerical procedure for calculating the irreducible 2-loop graphs of the sunset topology is presented. On the other hand, the chiral Lagrangian L (6) produces a direct coupling of the K 0 current with the electromagnetic field tensor. Due to this coupling one of the unknown parameters of L (6) occurs in the contribution…

Comment on "Total Cross Section for Photon Absorption by Two Protons inHe3"

1995

Cryogenic setup for trapped ion quantum computing

2016

We report on the design of a cryogenic setup for trapped ion quantum computing containing a segmented surface electrode trap. The heat shield of our cryostat is designed to attenuate alternating magnetic field noise, resulting in 120~dB reduction of 50~Hz noise along the magnetic field axis. We combine this efficient magnetic shielding with high optical access required for single ion addressing as well as for efficient state detection by placing two lenses each with numerical aperture 0.23 inside the inner heat shield. The cryostat design incorporates vibration isolation to avoid decoherence of optical qubits due to the motion of the cryostat. We measure vibrations of the cryostat of less t…