64,010 research outputs found
Experimental Observation of Quantum Correlations in Modular Variables
We experimentally detect entanglement in modular position and momentum
variables of photon pairs which have passed through -slit apertures. We
first employ an entanglement criteria recently proposed in [Phys. Rev. Lett.
{\bf 106}, 210501 (2011)], using variances of the modular variables. We then
propose an entanglement witness for modular variables based on the Shannon
entropy, and test it experimentally. Finally, we derive criteria for
Einstein-Podolsky-Rosen-Steering correlations using variances and entropy
functions. In both cases, the entropic criteria are more successful at
identifying quantum correlations in our data.Comment: 7 pages, 4 figures, comments welcom
Minimax signal detection in ill-posed inverse problems
Ill-posed inverse problems arise in various scientific fields. We consider
the signal detection problem for mildly, severely and extremely ill-posed
inverse problems with -ellipsoids (bodies), , for Sobolev,
analytic and generalized analytic classes of functions under the Gaussian white
noise model. We study both rate and sharp asymptotics for the error
probabilities in the minimax setup. By construction, the derived tests are,
often, nonadaptive. Minimax rate-optimal adaptive tests of rather simple
structure are also constructed.Comment: Published in at http://dx.doi.org/10.1214/12-AOS1011 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Josephson-vortex-flow terahertz emission in layered high- superconducting single crystals
We report on the successful terahertz emission (0.61 THz) that is
continuous and tunable in its frequency and power, by driving Josephson
vortices in resonance with the collective standing Josephson plasma modes
excited in stacked BiSrCaCuO intrinsic Josephson junctions.
Shapiro-step detection was employed to confirm the terahertz-wave emission. Our
results provide a strong feasibility of developing long-sought solid-state
terahertz-wave emission devices
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