21,734 research outputs found
Vibration responses of test structure no. 1 during the Edwards Air Force Base phase of the national sonic boom program
In order to evaluate reaction of people to sonic booms of varying overpressures and time durations, a series of closely controlled and systematic flight test studies were conducted in the vicinity of Edwards AFB, California, from June 3 to June 23, 1966. The dynamic responses of several building structures were measured as a part of these studies, and the measurements made in a one-story residence structure (Edwards test structure No. 1) are presented. Sample acceleration and strain recordings are presented from F-104, B-58, and XB-70 sonic-boom exposures, along with tabulations of the maximum acceleration and strain values measured for each one of about 140 flight tests. These data are compared with similar measurements for engine noise exposures of the building during simulated landing approaches and takeoffs of KC-135 aircraft
A research program to reduce interior noise in general aviation airplanes. Design of an acoustic panel test facility
The design, construction, and costs of a test facility for determining the sound transmission loss characteristics of various panels and panel treatments are described. The pressurization system and electronic equipment used in experimental testing are discussed as well as the reliability of the facility and the data gathered. Tests results are compared to pertinent acoustical theories for panel behavior and minor anomalies in the data are examined. A method for predicting panel behavior in the stiffness region is also presented
Variability in sonic-boom signatures measured along an 8000-foot linear array
Variability in sonic boom signatures measured along 8000 foot linear microphone arra
Classical, quantum and total correlations
We discuss the problem of separating consistently the total correlations in a
bipartite quantum state into a quantum and a purely classical part. A measure
of classical correlations is proposed and its properties are explored.Comment: 10 pages, 3 figure
Foundations of Quantum Discord
This paper summarizes the basics of the notion of quantum discord and how it
relates to other types of correlations in quantum physics. We take the
fundamental information theoretic approach and illustrate our exposition with a
number of simple examples.Comment: 3 pages, special issue edited by Diogo de Oliveira Soares Pinto et a
Quantum quenches of ion Coulomb crystals across structural instabilities
Quenches in an ion chain can create coherent superpositions of motional
states across the linear-zigzag structural transition. The procedure has been
described in [Phys. Rev. A 84, 063821 (2011)] and makes use of spin-dependent
forces, so that a coherent superposition of the electronic states of one ion
evolves into an entangled state between the chain's internal and external
degrees of freedom. The properties of the crystalline state so generated are
theoretically studied by means of Ramsey interferometry on one ion of the
chain. An analytical expression for the visibility of the interferometric
measurement is obtained for a chain of arbitrary number of ions and as a
function of the time elapsed after the quench. Sufficiently close to the
linear-zigzag instability the visibility decays very fast, but exhibits
revivals at the period of oscillation of the mode that drives the structural
instability. These revivals have a periodicity that is independent of the
crystal size, and they signal the creation of entanglement by the quantum
quench.Comment: 14 pages, 8 figures; added a paragraph in the introduction providing
more background, added paragraph at the end of Sec. IV discussing
experimental parameter
Macromolecular structural dynamics visualized by pulsed dose control in 4D electron microscopy
Macromolecular conformation dynamics, which span a wide range of time scales, are fundamental to the understanding of properties and functions of their structures. Here, we report direct imaging of structural dynamics of helical macromolecules over the time scales of conformational dynamics (ns to subsecond) by means of four-dimensional (4D) electron microscopy in the single-pulse and stroboscopic modes. With temporally controlled electron dosage, both diffraction and real-space images are obtained without irreversible radiation damage. In this way, the order-disorder transition is revealed for the organic chain polymer. Through a series of equilibrium-temperature and temperature-jump dependencies, it is shown that the metastable structures and entropy of conformations can be mapped in the nonequilibrium region of a “funnel-like” free-energy landscape. The T-jump is introduced through a substrate (a “hot plate” type arrangement) because only the substrate is made to absorb the pulsed energy. These results illustrate the promise of ultrafast 4D imaging for other applications in the study of polymer physics as well as in the visualization of biological phenomena
Invariant quantum discord in qubit-qutrit systems under local dephasing
We investigate the dynamics of quantum discord and entanglement for a
class of mixed qubit-qutrit states assuming that only the qutrit is under the action of a dephasing channel. We demonstrate that even though the entanglement in the qubit-qutrit state disappears in a finite time interval, partial coherence left in the system enables quantum discord to remain invariant throughout the whole time evolution
The elusive source of quantum effectiveness
We discuss two qualities of quantum systems: various correlations existing
between their subsystems and the distingushability of different quantum states.
This is then applied to analysing quantum information processing. While quantum
correlations, or entanglement, are clearly of paramount importance for
efficient pure state manipulations, mixed states present a much richer arena
and reveal a more subtle interplay between correlations and distinguishability.
The current work explores a number of issues related with identifying the
important ingredients needed for quantum information processing. We discuss the
Deutsch-Jozsa algorithm, the Shor algorithm, the Grover algorithm and the power
of a single qubit class of algorithms. One section is dedicated to cluster
states where entanglement is crucial, but its precise role is highly
counter-intuitive. Here we see that distinguishability becomes a more useful
concept.Comment: 8 pages, no figure
Teleportation as a Depolarizing Quantum Channel, Relative Entropy and Classical Capacity
We show that standard teleportation with an arbitrary mixed state resource is
equivalent to a generalized depolarizing channel with probabilities given by
the maximally entangled components of the resource. This enables the usage of
any quantum channel as a generalized depolarizing channel without additional
twirling operations. It also provides a nontrivial upper bound on the
entanglement of a class of mixed states. Our result allows a consistent and
statistically motivated quantification of teleportation success in terms of the
relative entropy and this quantification can be related to a classical
capacity.Comment: Version published in Phys. Rev. Let
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