31,933 research outputs found
Experimental determination of a nonclassical Glauber-Sudarshan P function
A quantum state is nonclassical if its Glauber-Sudarshan P function fails to
be interpreted as a probability density. This quantity is often highly
singular, so that its reconstruction is a demanding task. Here we present the
experimental determination of a well-behaved P function showing negativities
for a single-photon-added thermal state. This is a direct visualization of the
original definition of nonclassicality. The method can be useful under
conditions for which many other signatures of nonclassicality would not
persist.Comment: 4 pages, 4 figure
Tool pre-tensions covers prior to lacing
In securing a bulky object in a storage compartment, a cinching or tightening tool is used to draw two opposing cover halves together at a predetermined tension to permit quick lacing to retain the stored object. This tool is also useful in fabrication industries to draw components together during assembly or treating
Space shuttle navigation analysis. Volume 1: GPS aided navigation
Analytical studies related to space shuttle navigation are presented. Studies related to the addition of NAVSTAR Global Positioning System user equipment to the shuttle avionics suite are presented. The GPS studies center about navigation accuracy covariance analyses for both developmental and operational phases of GPS, as well as for various orbiter mission phases
2H and 13C NMR studies on the temperature-dependent water and protein dynamics in hydrated elastin, myoglobin and collagen
2H NMR spin-lattice relaxation and line-shape analyses are performed to study
the temperature-dependent dynamics of water in the hydration shells of
myoglobin, elastin, and collagen
Radiative corrections in neutrino-deuterium disintegration
The radiative corrections of order alpha for the charged- and neutral-current neutrino-deuterium disintegration for energies relevant to the SNO experiment are evaluated. Particular attention is paid to the issue of the bremsstrahlung detection threshold. It is shown that the radiative corrections to the total cross section for the charged current reaction are independent of that threshold, as they must be for consistency, and amount to a slowly decreasing function of the neutrino energy E-nu, varying from about 4% at low energies to 3% at the end of the B-8 spectrum. The differential cross section corrections, on the other hand, do depend on the bremsstrahlung detection threshold. Various choices of the threshold are discussed. It is shown that for a realistic choice of the threshold and for the actual electron energy threshold of the SNO detector, the deduced B-8 nu(e) flux should be decreased by about 2%. The radiative corrections to the neutral-current reaction are also evaluated
Necessary and sufficient conditions for bipartite entanglement
Necessary and sufficient conditions for bipartite entanglement are derived,
which apply to arbitrary Hilbert spaces. Motivated by the concept of witnesses,
optimized entanglement inequalities are formulated solely in terms of arbitrary
Hermitian operators, which makes them useful for applications in experiments.
The needed optimization procedure is based on a separability eigenvalue
problem, whose analytical solutions are derived for a special class of
projection operators. For general Hermitian operators, a numerical
implementation of entanglement tests is proposed. It is also shown how to
identify bound entangled states with positive partial transposition.Comment: 7 pages, 2 figur
Nonclassicality filters and quasiprobabilities
Necessary and sufficient conditions for the nonclassicality of bosonic
quantum states are formulated by introducing nonclassicality filters and
nonclassicality quasiprobability distributions. Regular quasiprobabilities are
constructed from characteristic functions which can be directly sampled by
balanced homodyne detection. Their negativities uncover the nonclassical
effects of general quantum states. The method is illustrated by visualizing the
nonclassical nature of a squeezed state.Comment: Significantly revised version, more emphasis on practical applicatio
Quantum-state extraction from high-Q cavities
The problem of extraction of a single-mode quantum state from a high-Q cavity
is studied for the case in which the time of preparation of the quantum state
of the cavity mode is short compared with its decay time. The temporal
evolution of the quantum state of the field escaping from the cavity is
calculated in terms of phase-space functions. A general condition is derived
under which the quantum state of the pulse built up outside the cavity is a
nearly perfect copy of the quantum state the cavity field was initially
prepared in. The results show that unwanted losses prevent the realization of a
nearly perfect extraction of nonclassical quantum states from high-Q optical
microcavities with presently available technology.Comment: RevTeX4, 9 pages with 6 figures; extended version as submitted to
Phys. Rev.
Nanometers-thick self-organized Fe stripes: bridging the gap between surfaces and magnetic materials
We have fabricated 5nm-high Fe(110) stripes by self-organized (SO) growth on
a slightly vicinal R(110)/Al2O3(11-20) surface, with R=Mo, W. Remanence,
coercivity and domain patterns were observed at room temperature (RT). This
contrasts with conventional SO epitaxial systems, that are superparamagnetic or
even non-magnetic at RT due to their flatness. Our process should help to
overcome superparamagnetism without compromise on the lateral size if SO
systems are ever to be used in applications
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