4,955 research outputs found
Classical Bound for Mach-Zehnder Super-Resolution
The employment of path entangled multiphoton states enables measurement of
phase with enhanced precision. It is common practice to demonstrate the unique
properties of such quantum states by measuring super-resolving oscillations in
the coincidence rate of a Mach-Zehnder interferometer. Similar oscillations,
however, have also been demonstrated in various configurations using classical
light only; making it unclear what, if any, are the classical limits of this
phenomenon. Here we derive a classical bound for the visibility of
super-resolving oscillations in a Mach-Zehnder. This provides an easy to apply,
fundamental test of non-classicality. We apply this test to experimental
multiphoton coincidence measurements obtained using photon number resolving
detectors. Mach-Zehnder super-resolution is found to be a highly distinctive
quantum effect.Comment: 4 pages, 4 figure, Comments welcom
Two-photon path-entangled states in multi-mode waveguides
We experimentally show that two-photon path-entangled states can be
coherently manipulated by multi-mode interference in multi-mode waveguides. By
measuring the output two-photon spatial correlation function versus the phase
of the input state, we show that multi-mode waveguides perform as nearly-ideal
multi-port beam splitters at the quantum level, creating a large variety of
entangled and separable multi-path two-photon states.Comment: 4 pages, 4 figure
Compressive ghost imaging
We describe an advanced image reconstruction algorithm for pseudothermal
ghost imaging, reducing the number of measurements required for image recovery
by an order of magnitude. The algorithm is based on compressed sensing, a
technique that enables the reconstruction of an N-pixel image from much less
than N measurements. We demonstrate the algorithm using experimental data from
a pseudothermal ghost-imaging setup. The algorithm can be applied to data taken
from past pseudothermal ghost-imaging experiments, improving the
reconstruction's quality.Comment: Comments are welcom
High-energy neutrinos from a lunar observatory
The detection of high-energy (HE) cosmic and solar-flare neutrions near the lunar surface would be feasible at energies much lower than for a terrestrial observatory. At these lower energies ( 10 to the 9th eV), the neutrino background is drastically reduced below that generated by cosmic rays in the Earth's atmosphere. Because of the short mean free path ( 1m) of the progenitor pi and K mesons against nuclear interactions in lunar rocks, the neutrino background would be quite low. At 1 GeV, less than 1% of the pions would decay; at 10 GeV, 0.1%. Thus, if the neutrino flux to be observed is intense enough, and its spectrum is steep enough, then the signal-to-noise ratio is very favorable. The observation of HE neutrinos from solar flares would be dramatically enhanced, especially at lower energies, since the flare spectra are very steep. Detection of these neutrinos on Earth does not appear to be feasible. A remarkable feature of solar flares as viewed in HE neutrinos from a lunar base is that the entire surface of the Sun would be visible
GRO source candidates: (A) Nearby modest-size molecular clouds; (B) Pulsar with Wolf-Rayet companion that has lost its H-envelope
Within 100 pc of the sun there are over a hundred cirrus clouds with masses of approx. 60 solar mass and dense molecular clouds with masses of approx. 4 solar mass. If the local interstellar density of cosmic rays is also present in these clouds, the flux of neutral pion from the decay of gamma rays from the core of a cloud at a distance of 20 pc is approx. 13 x 10(exp -8) photons/sq cm/s. The flux from the more extensive cirrus cloud is approx 4 x 10(exp -7) photons/sq cm/s. A relativistic beam of particles generated by a compact stellar object and incident upon a large, close companion can be a strong gamma ray line source if more of the beam energy is used in interactions with C and O and heavier nuclei and less with H and He. This would be the case if the companion has lost its hydrogen envelope and nucleosynthesized much of its He into C, O, and Ne. Such objects are Wolf-Rayet stars and it is believed that some Wolf-Rayet stars do, in fact, have compact companions. For a beam of protons of 10(exp 37) erg/s, the flux at 1 kpc of the 4.4 MeV C-12 line could be as high as 5 x 10(exp -6) photons/sq cm/s. The fluxes of the deexcitation lines from the spallation products of O-16 are also presented
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