237 research outputs found
Longer-Baseline Telescopes Using Quantum Repeaters
We present an approach to building interferometric telescopes using ideas of
quantum information. Current optical interferometers have limited baseline
lengths, and thus limited resolution, because of noise and loss of signal due
to the transmission of photons between the telescopes. The technology of
quantum repeaters has the potential to eliminate this limit, allowing in
principle interferometers with arbitrarily long baselines.Comment: 10 pages, v2 improved clarit
A wavelength-tunable fiber-coupled source of narrowband entangled photons
We demonstrate a wavelength-tunable, fiber-coupled source of
polarization-entangled photons with extremely high spectral brightness and
quality of entanglement. Using a 25 mm PPKTP crystal inside a polarization
Sagnac interferometer we detect a spectral brightness of 273000 pairs/(s mW
nm), a factor of 28 better than comparable previous sources while state
tomography showed the two-photon state to have a tangle of T=0.987. This
improvement was achieved by use of a long crystal, careful selection of
focusing parameters and single-mode fiber coupling. We demonstrate that, due to
the particular geometry of the setup, the signal and idler wavelengths can be
tuned over a wide range without loss of entanglement.Comment: 10 pages, 5 figures. Article rewritten, added Fig.(1a-1b). Published
in Optics Express, comments welcom
Is wave-particle objectivity compatible with determinism and locality?
Wave-particle duality, superposition and entanglement are among the most
counterintuitive features of quantum theory. Their clash with our classical
expectations motivated hidden-variable (HV) theories. With the emergence of
quantum technologies we can test experimentally the predictions of quantum
theory {\em versus} HV theories and put strong restrictions on their key
assumptions. Here we study an entanglement-assisted version of the quantum
delayed-choice experiment and show that the extension of HV to the controlling
devices only exacerbates the contradiction. We compare HV theories that satisfy
the conditions of objectivity (a property of photons being either particles or
waves, but not both), determinism, and local independence of hidden variables
with quantum mechanics. Any two of the above conditions are compatible with it.
The conflict becomes manifest when all three conditions are imposed and
persists for any non-zero value of entanglement. We propose an experiment to
test our conclusions.Comment: A published version. The logic is similar to the original version,
but many changes were introduce
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