91,375 research outputs found
When a quantum measurement can be implemented locally ... and when it cannot
Local operations on subsystems and classical communication between parties
(LOCC) constitute the most general protocols available on spatially separated
quantum systems. Every LOCC protocol implements a separable generalized
measurement -- a complete measurement for which every outcome corresponds to a
tensor product of operators on individual subsystems -- but it is known that
there exist separable measurements that cannot be implemented by LOCC. A
longstanding problem in quantum information theory is to understand the
difference between LOCC and the full set of separable measurements. In this
paper, we show how to construct an LOCC protocol to implement an arbitrary
separable measurement, except that with those measurements for which no LOCC
protocol exists, the method shows explicitly that this is the case.Comment: 21 pages, 7 figures. Extensively revised to include details of all
arguments, explicitly proving all results in full rigor. Version 3 has
sections reordered and other restructuring, but otherwise contains the same
discussion as version
Civic Engagement and Service Learning Partnerships
Service learning is designed to promote volunteerism and civic awareness. Community engagement in higher education specifically involves university members partnering with local community organizations to address a need. Students engage with community partners through service learning and other activities (Moore & Mendez, 2014). Service learning is a practice that connects new knowledge and social responsibility through active learning (Benson & Younkin, 1996).https://digitalscholarship.unlv.edu/btp_expo/1083/thumbnail.jp
Phase boundaries in deterministic dense coding
We consider dense coding with partially entangled states on bipartite systems
of dimension , studying the conditions under which a given number of
messages, , can be deterministically transmitted. It is known that the
largest Schmidt coefficient, , must obey the bound , and considerable empirical evidence points to the conclusion that there
exist states satisfying for every and except the
special cases and . We provide additional conditions under
which this bound cannot be reached -- that is, when it must be that
-- yielding insight into the shapes of boundaries separating
entangled states that allow messages from those that allow only . We
also show that these conclusions hold no matter what operations are used for
the encoding, and in so doing, identify circumstances under which unitary
encoding is strictly better than non-unitary.Comment: 7 pages, 1 figur
Detection of atomic entanglement and electromagnetically induced transparency in velocity-selective coherent population trapping
We investigate theoretically the optical properties of an atomic gas which
has been cooled by the laser cooling method velocity-selective coherent
population trapping. We demonstrate that the application of a weak laser pulse
gives rise to a backscattered pulse, which is a direct signal for the
entanglement in the atomic system, and which leads to single-particle
entanglement on the few-photon level. If the pulse is applied together with the
pump lasers, it also displays the phenomenon of electromagnetically induced
transparency. We suggest that the effect should be observable in a gas of
Rubidium atoms.Comment: Revtex, 9 pages, 6 figures. To appear in Physical Review
Characteristics of the dynamics of breakdown filaments in Al2O3/InGaAs stacks
In this paper, the Al2O3/InGaAs interface was studied by X-ray photoelectron spectroscopy (XPS) after a breakdown (BD) event at positive bias applied to the gate contact. The dynamics of the BD event were studied by comparable XPS measurements with different current compliance levels during the BD event. The overall results show that indium atoms from the substrate move towards the oxide by an electro-migration process and oxidize upon arrival following a power law dependence on the current compliance of the BD event. Such a result reveals the physical feature of the breakdown characteristics of III-V based metal-oxide-semiconductor devices.Fil: Palumbo, Félix Roberto Mario. Comisión Nacional de Energía Atómica; Argentina. Universidad Tecnológica Nacional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Shekhter, P.. Technion - Israel Institute of Technology; IsraelFil: Cohen Weinfeld, K.. Technion - Israel Institute of Technology; IsraelFil: Eizenberg, M.. Technion - Israel Institute of Technology; Israe
Vortices Clustering: The Origin of the Second Peak in the Magnetisation Loops of High Temperature Superconductors
We study vortex clustering in type II Superconductors. We demonstrate that
the ``second peak'' observed in magnetisation loops may be a dynamical effect
associated with a density driven instability of the vortex system. At the
microscopic level the instability shows up as the clustering of individual
vortices at (rare) preferential regions of the pinning potential. In the limit
of quasi-static ramping the instability is related to a phase transition in the
equilibrium vortex system.Comment: 11 pages + 3 figure
Diagnostics Of Disks Around Hot Stars
We discuss three different observational diagnostics related to disks around hot stars: absorption line determinations of rotational velocities of Be stars; polarization diagnostics of circumstellar disks; and X-ray line diagnostics of one specific magnetized hot star, theta(1) Ori C. Some common themes that emerge from these studies include (a) the benefits of having a specific physical model as a framework for interpreting diagnostic data; (b) the importance of combining several different types of observational diagnostics of the same objects; and (c) that while there is often the need to reinterpret traditional diagnostics in light of new theoretical advances, there are many new and powerful diagnostics that are, or will soon be, available for the study of disks around hot stars
Cooperative effects in Josephson junctions in a cavity in the strong coupling regime
We analyze the behavior of systems of two and three qubits made by Josephson
junctions, treated in the two level approximation, driven by a radiation mode
in a cavity. The regime we consider is a strong coupling one recently
experimentally reached for a single junction. Rabi oscillations are obtained
with the frequency proportional to integer order Bessel functions in the limit
of a large photon number, similarly to the case of the single qubit. A
selection rule is derived for the appearance of Rabi oscillations. A quantum
amplifier built with a large number of Josephson junctions in a cavity in the
strong coupling regime is also described.Comment: 9 pages, no figures. Version accepted for publication in Physical
Review
Energy diffusion in frustrated quantum spin chains exhibiting Gaussian orthogonal ensemble level statistics
Frustrated quantum spin chains with the next-nearest-neighbor (NNN)
couplings are typically deterministic many-body systems exhibiting Gaussian
orthogonal ensemble (GOE) spectral statistics. We investigate energy diffusion
for these spin chains in the presence of a periodically oscillating magnetic
field. Diffusion coefficients are found to obey the power law with respect to
both the field strength and driving frequency with its power varying depending
on the linear response and non-perturbative regimes. The widths of the linear
response and the non-perturbative regimes depend on the strength of
frustrations. We have also elucidated a mechanism for oscillation of energy
diffusion in the case of weakened frustrations.Comment: 6 pages, 6 figure
Sheath ionization model of beam emissions from large spacecraft
An analytical model of the charging of a spacecraft emitting electron and ion beams has been applied to the case of large spacecraft. In this model, ionization occurs in the sheath due to the return current. Charge neutralization of spherical space charge flow is examined by solving analytical equations numerically. Parametric studies of potential large spacecraft are performed. As in the case of small spacecraft, the ions created in the sheath by the returning current play a large role in determining spacecraft potential
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