81,962 research outputs found
Quantifying nonorthogonality
An exploratory approach to the possibility of analyzing nonorthogonality as a
quantifiable property is presented. Three different measures for the
nonorthogonality of pure states are introduced, and one of these measures is
extended to single-particle density matrices using methods that are similar to
recently introduced techniques for quantifying entanglement. Several
interesting special cases are considered. It is pointed out that a measure of
nonorthogonality can meaningfully be associated with a single mixed quantum
state. It is then shown how nonorthogonality can be unlocked with classical
information; this analysis reveals interesting inequalities and points to a
number of connections between nonorthogonality and entanglement.Comment: Accepted for publication in Phys. Rev.
On a nonlinear theory of elastic shells
Nonlinear theory of elastic shells with deformation gradient
Space Station Human Factors Research Review. Volume 1: EVA Research and Development
An overview is presented of extravehicular activity (EVA) research and development activities at Ames. The majority of the program was devoted to presentations by the three contractors working in parallel on the EVA System Phase A Study, focusing on Implications for Man-Systems Design. Overhead visuals are included for a mission results summary, space station EVA requirements and interface accommodations summary, human productivity study cross-task coordination, and advanced EVAS Phase A study implications for man-systems design. Articles are also included on subsea approach to work systems development and advanced EVA system design requirements
Diagnosis of antiphospholipid syndrome in routine clinical practice.
The updated international consensus criteria for definite antiphospholipid syndrome (APS) are useful for scientific clinical studies. However, there remains a need for diagnostic criteria for routine clinical use. We audited the results of routine antiphospholipid antibodies (aPLs) in a cohort of 193 consecutive patients with aPL positivity-based testing for lupus anticoagulant (LA), IgG and IgM anticardiolipin (aCL) and anti-ß(2)glycoprotein-1 antibodies (aß(2)GPI). Medium/high-titre aCL/aβ(2)GPI was defined as >99th percentile. Low-titre aCL/aβ(2)GPI positivity (>95(th )< 99(th) percentile) was considered positive for obstetric but not for thrombotic APS. One hundred of the 145 patients fulfilled both clinical and laboratory criteria for definite APS. Twenty-six women with purely obstetric APS had persistent low-titre aCL and/or aβ(2)GPI. With the inclusion of these patients, 126 of the 145 patients were considered to have APS. Sixty-seven out of 126 patients were LA-negative, of whom 12 had aCL only, 37 had aβ(2)GPI only and 18 positive were for both. The omission of aCL or aβ(2)GPI testing from investigation of APS would have led to a failure to diagnose APS in 9.5% and 29.4% of patients, respectively. Our data suggest that LA, aCL and aβ(2)GPI testing are all required for the accurate diagnosis of APS and that low-titre antibodies should be included in the diagnosis of obstetric APS
Generation of atom-atom correlations inside and outside the mutual light cone
We analyze whether a pair of neutral two level atoms can become entangled in
a finite time while they remain causally disconnected. The interaction with the
e. m. field is treated perturbatively in the electric dipole approximation. We
start from an initial vacuum state and obtain the final atomic correlations for
the cases where n = 0, 1, or 2 photons are produced in a time t, and also when
the final field state is unknown. Our results show that correlations are
sizable inside and outside the mutual light cone for n= 1 and 2, and also that
quantum correlations become classical by tracing over the field state. For n =
0 we obtain entanglement generation by photon propagation between the atoms,
the correlations come from the indistinguishability of the source for n = 1,
and may give rise to entanglement swapping for n = 2.Comment: v2: Minor changes, references added. v3: full revision, appendix
added. v4: Minor changes. Accepted in Phys. Rev.
The MICZ-Kepler Problems in All Dimensions
The Kepler problem is a physical problem about two bodies which attract each
other by a force proportional to the inverse square of the distance. The
MICZ-Kepler problems are its natural cousins and have been previously
generalized from dimension three to dimension five. In this paper, we construct
and analyze the (quantum) MICZ-Kepler problems in all dimensions higher than
two.Comment: A minor technical error in section 5.2 (see footnote 6) is correcte
Measurement of the ac Stark shift with a guided matter-wave interferometer
We demonstrate the effectiveness of a guided-wave Bose-Einstein condensate
interferometer for practical measurements. Taking advantage of the large arm
separations obtainable in our interferometer, the energy levels of the 87Rb
atoms in one arm of the interferometer are shifted by a calibrated laser beam.
The resulting phase shifts are used to determine the ac polarizability at a
range of frequencies near and at the atomic resonance. The measured values are
in good agreement with theoretical expectations. However, we observe a
broadening of the transition near the resonance, an indication of collective
light scattering effects. This nonlinearity may prove useful for the production
and control of squeezed quantum states.Comment: 5 pages, three figure
Dynamics of the collective modes of an inhomogeneous spin ensemble in a cavity
We study the excitation dynamics of an inhomogeneously broadened spin
ensemble coupled to a single cavity mode. The collective excitations of the
spin ensemble can be described in terms of generalized spin waves and, in the
absence of the cavity, the free evolution of the spin ensemble can be described
as a drift in the wave number without dispersion. In this article we show that
the dynamics in the presence of coupling to the cavity mode can be described
solely by a modified time evolution of the wave numbers. In particular, we show
that collective excitations with a well- defined wave number pass without
dispersion from negative to positive valued wave numbers without populating the
zero wave number spin wave mode. The results are relevant for multi-mode
collective quantum memories where qubits are encoded in different spin waves.Comment: Published version. Some small changes and correction
Probing multipartite entanglement in a coupled Jaynes-Cummings system
We show how to probe multipartite entanglement in coupled Jaynes-Cummings
cells where the degrees of freedom are the electronic energies of each of the
atoms in separate single-mode cavities plus the single-mode fields
themselves. Specifically we propose probing the combined system as though it is
a dielectric medium. The spectral properties and transition rates directly
reveal multipartite entanglement signatures. It is found that the Hilbert space
of the cell system can be confined to the totally symmetric subspace of two
states only that are maximally-entangled W states with 2N degrees of freedom
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