5,397 research outputs found
Development of a container for handling, testing, and storing discrete microelectronic components
A container has been developed for handling, testing, burning-in, and storing discrete microelectronic components without removal from the protective package. The package was designed to accommodate the leadless inverted device and other carrier-mounted active devices and chip-type discrete resistors and capacitors. Before the indicated development, components were handled and tested in various ways, some of which resulted in damage or contamination. The basic design of the container utilizes precision machined printed circuit boards and chemically milled (photoetched) contact springs. Included in this design for protection is an O-ring-sealed cover. Methods of fabrication and limitations of the current hardware are presented. Current applications of and possible extensions to the technology are discussed
Squeezed state purification with linear optics and feed forward
A scheme for optimal and deterministic linear optical purification of mixed
squeezed Gaussian states is proposed and experimentally demonstrated. The
scheme requires only linear optical elements and homodyne detectors, and allows
the balance between purification efficacy and squeezing degradation to be
controlled. One particular choice of parameters gave a ten-fold reduction of
the thermal noise with a corresponding squeezing degradation of only 11%. We
prove optimality of the protocol, and show that it can be used to enhance the
performance of quantum informational protocols such as dense coding and
entanglement generation.Comment: 4 pages, 3 figure
Action minimizing fronts in general FPU-type chains
We study atomic chains with nonlinear nearest neighbour interactions and
prove the existence of fronts (heteroclinic travelling waves with constant
asymptotic states). Generalizing recent results of Herrmann and Rademacher we
allow for non-convex interaction potentials and find fronts with non-monotone
profile. These fronts minimize an action integral and can only exists if the
asymptotic states fulfil the macroscopic constraints and if the interaction
potential satisfies a geometric graph condition. Finally, we illustrate our
findings by numerical simulations.Comment: 19 pages, several figure
Nonunity gain minimal-disturbance measurement
We propose and experimentally demonstrate an optimal non-unity gain Gaussian
scheme for partial measurement of an unknown coherent state that causes minimal
disturbance of the state. The information gain and the state disturbance are
quantified by the noise added to the measurement outcomes and to the output
state, respectively. We derive the optimal trade-off relation between the two
noises and we show that the trade-off is saturated by non-unity gain
teleportation. Optimal partial measurement is demonstrated experimentally using
a linear optics scheme with feed-forward.Comment: 12 page
Environmental Assisted Quantum Information Correction for Continuous Variables
Quantum information protocols are inevitably affected by decoherence which is
associated with the leakage of quantum information into an environment. In this
paper we address the possibility of recovering the quantum information from an
environmental measurement. We investigate continuous variable quantum
information, and we propose a simple environmental measurement that under
certain circumstances fully restores the quantum information of the signal
state although the state is not reconstructed with unit fidelity. We implement
the protocol for which information is encoded into conjugate quadratures of
coherent states of light and the noise added under the decoherence process is
of Gaussian nature. The correction protocol is tested using both a
deterministic as well as a probabilistic strategy. The potential use of the
protocol in a continuous variable quantum key distribution scheme as a means to
combat excess noise is also investigated.Comment: Submitted to PR
Self-compensation in semiconductors: The Zn vacancy in Ga-doped ZnO
Self-compensation, the tendency of a crystal to lower its energy by forming point defects to counter the effects of a dopant, is here quantitatively proven. Based on a new theoretical formalism and several different experimental techniques, we demonstrate that the addition of 1.4 Ă 10 exp 21-cm exp â3 Ga donors in ZnO causes the lattice to form 1.7 Ă 10 exp 20-cm exp â3 Zn-vacancy acceptors. The calculated VZn formation energy of 0.2 eV is consistent with predictions from density functional theory. Our formalism is of general validity and can be used to investigate self-compensation in any degenerate semiconductor material.Peer reviewe
Purity of Gaussian states: measurement schemes and time-evolution in noisy channels
We present a systematic study of the purity for Gaussian states of
single-mode continuous variable systems. We prove the connection of purity to
observable quantities for these states, and show that the joint measurement of
two conjugate quadratures is necessary and sufficient to determine the purity
at any time. The statistical reliability and the range of applicability of the
proposed measurement scheme is tested by means of Monte Carlo simulated
experiments. We then consider the dynamics of purity in noisy channels. We
derive an evolution equation for the purity of general Gaussian states both in
thermal and squeezed thermal baths. We show that purity is maximized at any
given time for an initial coherent state evolving in a thermal bath, or for an
initial squeezed state evolving in a squeezed thermal bath whose asymptotic
squeezing is orthogonal to that of the input state.Comment: 9 Pages, 6 Figures; minor errors correcte
Quantum filtering of optical coherent states
We propose and experimentally demonstrate nondestructive and noiseless removal (filtering) of vacuum states from an arbitrary set of coherent states of continuous variable systems. Errors, i.e., vacuum states in the quantum information are diagnosed through a weak measurement, and on that basis, probabilistically filtered out. We consider three different filters based on on-off detection, phase stabilized, and phase randomized homodyne detection. We find that on-off detection, optimal in the ideal theoretical setting, is superior to the homodyne strategy also in a practical setting
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