1,829 research outputs found
Fundamental length in quantum theories with PT-symmetric Hamiltonians
The direct observability of coordinates x is often lost in PT-symmetric
quantum theories. A manifestly non-local Hilbert-space metric enters
the double-integral normalization of wave functions there. In the
context of scattering, the (necessary) return to the asymptotically fully local
metric has been shown feasible, for certain family of PT-symmetric toy
Hamiltonians H at least, in paper I (M. Znojil, Phys. Rev. D 78 (2008) 025026).
Now we show that in a confined-motion dynamical regime the same toy model
proves also suitable for an explicit control of the measure or width
of its non-locality. For this purpose each H is assigned here, constructively,
the complete menu of its hermitizing metrics
distinguished by their optional "fundamental lengths" .
The local metric of paper I recurs at while the most popular
CPT-symmetric hermitization proves long-ranged, with .Comment: 31 pp, 3 figure
Gegenbauer-solvable quantum chain model
In an innovative inverse-problem construction the measured, experimental
energies , , ... of a quantum bound-state system are assumed
fitted by an N-plet of zeros of a classical orthogonal polynomial . We
reconstruct the underlying Hamiltonian (in the most elementary
nearest-neighbor-interaction form) and the underlying Hilbert space
of states (the rich menu of non-equivalent inner products is offered). The
Gegenbauer's ultraspherical polynomials are chosen for
the detailed illustration of technicalities.Comment: 29 pp., 1 fi
Simple manipulation of a microwave dressed-state ion qubit
Many schemes for implementing quantum information processing require that the atomic states used have a non-zero magnetic moment, however such magnetically sensitive states of an atom are vulnerable to decoherence due to fluctuating magnetic fields. Dressing an atom with an external field is a powerful method of reducing such decoherence [N. Timoney et al., Nature 476, 185], even if the states being dressed are strongly coupled to the environment. We introduce an experimentally simpler method of manipulating such a dressed-state qubit, which allows the implementation of general rotations of the qubit, and demonstrate this method using a trapped ytterbium ion
Scalable simultaneous multi-qubit readout with 99.99% single-shot fidelity
We describe single-shot readout of a trapped-ion multi-qubit register using
space and time-resolved camera detection. For a single qubit we measure
0.9(3)x10^{-4} readout error in 400us exposure time, limited by the qubit's
decay lifetime. For a four-qubit register (a "qunybble") we measure an
additional error of only 0.1(1)x10^{-4} per qubit, despite the presence of 4%
optical cross-talk between neighbouring qubits. A study of the cross-talk
indicates that the method would scale with negligible loss of fidelity to
~10000 qubits at a density <~1 qubit/um^2, with a readout time ~1us/qubit.Comment: 4 pages, 3 figures; simulations added to fig.3, with some further
text and figure revisions. Main results unchanged
A New Template Family For The Detection Of Gravitational Waves From Comparable Mass Black Hole Binaries
In order to improve the phasing of the comparable-mass waveform as we
approach the last stable orbit for a system, various re-summation methods have
been used to improve the standard post-Newtonian waveforms. In this work we
present a new family of templates for the detection of gravitational waves from
the inspiral of two comparable-mass black hole binaries. These new adiabatic
templates are based on re-expressing the derivative of the binding energy and
the gravitational wave flux functions in terms of shifted Chebyshev
polynomials. The Chebyshev polynomials are a useful tool in numerical methods
as they display the fastest convergence of any of the orthogonal polynomials.
In this case they are also particularly useful as they eliminate one of the
features that plagues the post-Newtonian expansion. The Chebyshev binding
energy now has information at all post-Newtonian orders, compared to the
post-Newtonian templates which only have information at full integer orders. In
this work, we compare both the post-Newtonian and Chebyshev templates against a
fiducially exact waveform. This waveform is constructed from a hybrid method of
using the test-mass results combined with the mass dependent parts of the
post-Newtonian expansions for the binding energy and flux functions. Our
results show that the Chebyshev templates achieve extremely high fitting
factors at all PN orders and provide excellent parameter extraction. We also
show that this new template family has a faster Cauchy convergence, gives a
better prediction of the position of the Last Stable Orbit and in general
recovers higher Signal-to-Noise ratios than the post-Newtonian templates.Comment: Final published version. Accepted for publication in Phys. Rev.
Quark-Gluon Jet Differences at LEP
A new method to identify the gluon jet in 3-jet ``{\bf Y}'' decays of
is presented. The method is based on differences in particle multiplicity
between quark jets and gluon jets, and is more effective than tagging by
leptonic decay. An experimental test of the method and its application to a
study of the ``string effect'' are proposed. Various jet-finding schemes for
3-jet events are compared.Comment: 11 pages, LaTeX, 4 PostScript figures availble from the author
([email protected]), MSUTH-92-0
Protocol for a national monthly survey of alcohol use in England with 6-month follow-up: 'The Alcohol Toolkit Study'.
Timely tracking of national patterns of alcohol consumption is needed to inform and evaluate strategies and policies aimed at reducing alcohol-related harm. Between 2014 until at least 2017, the Alcohol Toolkit Study (ATS) will provide such tracking data and link these with policy changes and campaigns. By virtue of its connection with the 'Smoking Toolkit Study' (STS), links will also be examined between alcohol and smoking-related behaviour
Exploring the Structure of Distant Galaxies with Adaptive Optics on the Keck-II Telescope
We report on the first observation of cosmologically distant field galaxies
with an high order Adaptive Optics (AO) system on an 8-10 meter class
telescope. Two galaxies were observed at 1.6 microns at an angular resolution
as high as 50 milliarcsec using the AO system on the Keck-II telescope. Radial
profiles of both objects are consistent with those of local spiral galaxies and
are decomposed into a classic exponential disk and a central bulge. A
star-forming cluster or companion galaxy as well as a compact core are detected
in one of the galaxies at a redshift of 0.37+/-0.05. We discuss possible
explanations for the core including a small bulge, a nuclear starburst, or an
active nucleus. The same galaxy shows a peak disk surface brightness that is
brighter than local disks of comparable size. These observations demonstrate
the power of AO to reveal details of the morphology of distant faint galaxies
and to explore galaxy evolution.Comment: 5 pages, Latex, 3 figures. Accepted for publication in P.A.S.
T-junction ion trap array for two-dimensional ion shuttling, storage and manipulation
We demonstrate a two-dimensional 11-zone ion trap array, where individual
laser-cooled atomic ions are stored, separated, shuttled, and swapped. The trap
geometry consists of two linear rf ion trap sections that are joined at a 90
degree angle to form a T-shaped structure. We shuttle a single ion around the
corners of the T-junction and swap the positions of two crystallized ions using
voltage sequences designed to accommodate the nontrivial electrical potential
near the junction. Full two-dimensional control of multiple ions demonstrated
in this system may be crucial for the realization of scalable ion trap quantum
computation and the implementation of quantum networks.Comment: 3 pages, 5 figure
Terrain-Moisture Classification Using GPS Surface-Reflected Signals
In this study we present a novel method of land surface classification using surface-reflected GPS signals in combination with digital imagery. Two GPS-derived classification features are merged with visible image data to create terrain-moisture (TM) classes, defined here as visibly identifiable terrain or landcover classes containing a surface/soil moisture component. As compared to using surface imagery alone, classification accuracy is significantly improved for a number of visible classes when adding the GPS-based signal features. Since the strength of the reflected GPS signal is proportional to the amount of moisture in the surface, use of these GPS features provides information about the surface that is not obtainable using visible wavelengths alone. Application areas include hydrology, precision agriculture, and wetlands mapping
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