28,111 research outputs found
Increasing and decreasing entanglement characteristics for continuous variables by a local photon subtraction
We investigate how the entanglement characteristics of a non-Gaussian
entangled state are increased or decreased by a local photon subtraction
operation. The non-Gaussian entangled state is generated by injecting a
single-mode non-Gaussian state and a vacuum state into a 50:50 beam splitter.
We consider a photon-added coherent state and an odd coherent state as a
single-mode non-Gaussian state. In the regime of small amplitude, we show that
the performance of quantum teleportation and the second-order
Einstein-Podolsky- Rosen-type correlation can both be enhanced, whereas the
degree of entanglement decreases, for the output state when a local photon
subtraction operation is applied to the non-Gaussian entangled state. The
counterintuitive effect is more prominent in the limit of nearly zero
amplitude.Comment: Published version, 7 pages, 3 figure
Financing Direct Democracy: Revisiting the Research on Campaign Spending and Citizen Initiatives
The conventional view in the direct democracy literature is that spending against a measure is more effective than spending in favor of a measure, but the empirical results underlying this conclusion have been questioned by recent research. We argue that the conventional finding is driven by the endogenous nature of campaign spending: initiative proponents spend more when their ballot measure is likely to fail. We address this endogeneity by using an instrumental variables approach to analyze a comprehensive dataset of ballot propositions in California from 1976 to 2004. We find that both support and opposition spending on citizen initiatives have strong, statistically significant, and countervailing effects. We confirm this finding by looking at time series data from early polling on a subset of these measures. Both analyses show that spending in favor of citizen initiatives substantially increases their chances of passage, just as opposition spending decreases this likelihood
Focusing RKKY interaction by graphene P-N junction
The carrier-mediated RKKY interaction between local spins plays an important
role for the application of magnetically doped graphene in spintronics and
quantum computation. Previous studies largely concentrate on the influence of
electronic states of uniform systems on the RKKY interaction. Here we reveal a
very different way to manipulate the RKKY interaction by showing that the
anomalous focusing - a well-known electron optics phenomenon in graphene P-N
junctions - can be utilized to refocus the massless Dirac electrons emanating
from one local spin to the other local spin. This gives rise to rich spatial
interference patterns and symmetry-protected non-oscillatory RKKY interaction
with a strongly enhanced magnitude. It may provide a new way to engineer the
long-range spin-spin interaction in graphene.Comment: 9 pages, 4 figure
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