2,593 research outputs found
Toward Spin Squeezing with Trapped Ions
Building robust instruments capable of making interferometric measurements
with precision beyond the standard quantum limit remains an important goal in
many metrology laboratories. We describe here the basic concepts underlying
spin squeezing experiments that allow one to surpass this limit. In priniciple
it is possible to reach the so-called Heisenberg limit, which constitutes an
improvement in precision by a factor , where is the number of
particles on which the measurement is carried out. In particular, we focus on
recent progress toward implementing spin squeezing with a cloud of beryllium
ions in a Penning ion trap, via the geometric phase gate used more commonly for
performing two-qubit entangling operations in quantum computing experiments.Comment: 18 pages, 9 figures, Contribution to Quantum Africa 2010 conference
proceeding
Mason Locke Weems, George Washington, and the Emergence of an Evangelical Nationalism in the Early Nineteenth Century
Why is a study of the past important to an understanding of nationalism? Webster defines nationalism as: a loyalty and devotion to a nation; especially : a sense of national consciousness exalting one nation above all others and placing primary emphasis on promotion of its culture and interests as opposed to those of other nations or supranational groups. 1 For most people, nationalism is an intense devotion to a particular nation. For some, nationalism produces an emotional attachment evoked by rituals or symbols such as a flag, a national anthem, or a royal family. Others view nationalism as a commonality one shares with a group of people who value a specific language, religion, political ideology, and basic framework of cultural principles above others. After a cursory examination of the development of nationalism in other countries, it is evident one of the most effective tools in creating such a feeling is a common history with which a group of people can identify.
Simulating Quantum Magnetism with Correlated Non-Neutral Ion Plasmas
By employing forces that depend on the internal electronic state (or spin) of
an atomic ion, the Coulomb potential energy of a strongly coupled array of ions
can be modified in a spin-dependent way to mimic effective quantum spin
Hamiltonians. Both ferromagnetic and antiferromagnetic interactions can be
implemented. We use simple models to explain how the effective spin
interactions are engineered with trapped-ion crystals. We summarize the type of
effective spin interactions that can be readily generated, and discuss an
experimental implementation using single-plane ion crystals in a Penning trap.Comment: 10 pages, 5 figures, to be published in the Proceedings of 10th
International Workshop on Non-Neutral Plasma
Frequency and time standards based on stored ions
The method of ion storage provides a basis for excellent time and frequency standards. This is due to the ability to confine ions for long periods of time without the usual perturbations associated with confinement (e.g., wall shifts). In addition, Doppler effects can be greatly suppressed. The use of stored ions for microwave frequency standards and the future possibilities for an optical frequency standard based on stored ions are addressed
Phase-coherent detection of an optical dipole force by Doppler velocimetry
We report phase-coherent Doppler detection of optical dipole forces using
large ion crystals in a Penning trap. The technique is based on laser Doppler
velocimetry using a cycling transition in Be near 313 nm and the
center-of-mass (COM) ion motional mode. The optical dipole force is tuned to
excite the COM mode, and measurements of photon arrival times synchronized with
the excitation potential show oscillations with a period commensurate with the
COM motional frequency. Experimental results compare well with a quantitative
model for a driven harmonic oscillator. This technique permits characterization
of motional modes in ion crystals; the measurement of both frequency and phase
information relative to the driving force is a key enabling capability --
comparable to lockin detection -- providing access to a parameter that is
typically not available in time-averaged measurements. This additional
information facilitates discrimination of nearly degenerate motional modes.Comment: Related manuscripts at http://www.physics.usyd.edu.au/~mbiercuk
Stress buildup in the Himalaya
The seismic cycle on a major fault involves long periods of elastic strain and stress accumulation, driven by aseismic ductile deformation at depth, ultimately released by sudden fault slip events. Coseismic slip distributions are generally heterogeneous with most of the energy being released in the rupture of asperities. Since, on the long term, the fault's walls generally do not accumulate any significant permanent deformation, interseismic deformation might be heterogeneous, revealing zones of focused stress buildup. The pattern of current deformation along the Himalayan arc, which is known to produce recurring devastating earthquakes, and where several seismic gaps have long been recognized, might accordingly show significant lateral variations, providing a possible explanation for the uneven microseismic activity along the Himalayan arc. By contrast, the geodetic measurements show a rather uniform pattern of interseismic strain, oriented consistently with long-term geological deformation, as indicated from stretching lineation. We show that the geodetic data and seismicity distribution are reconciled from a model in which microseismicity is interpreted as driven by stress buildup increase in the interseismic period. The uneven seismicity pattern is shown to reflect the impact of the topography on the stress field, indicating low deviatoric stresses (<35 MPa) and a low friction (<0.3) on the Main Himalayan Thrust. Arc-normal thrusting along the Himalayan front and east-west extension in southern Tibet are quantitatively reconciled by the model
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