John Bell’s theorem of 1964 states that local elements of physical reality, existing independent of measurement, are inconsistent with the predictions of quantum mechanics (Bell, J. S. (1964), Physics (College. Park. Md). Specifically, correlations between measurement results from distant entangled systems would be smaller than predicted by quantum physics. This is expressed in Bell’s inequalities. Employing modifications of Bell’s inequalities, many experiments have been performed that convincingly support the quantum predictions. Yet, all experiments rely on assumptions, which provide loopholes for a local realist explanation of the measurement. Here we report an experiment with polarization-entangled photons that simultaneously closes the most significant of these loopholes. We use a highly efficient source of entangled photons, distributed these over a distance of 58.5 meters, and implemented rapid random setting generation and high-efficiency detection to observe a violation of a Bell inequality with high statistical significance. The merely statistical probability of our results to occur under local realism is less than 3.74×10-31, corresponding to an 11.5 standard deviation effect.
We have examined ultrafast carrier dynamics and light amplification in ZnO nanowires following subpicosecond
excitation at room temperature. We performed time- and wavelength-resolved pump-probe transmission and gain
measurements on a 'forest' of 100- to 500-nm thick and 20-μm long nanowires, epitaxially grown on a sapphire wafer.
Measurements were done using 267-nm pump pulses for direct, but inhomogeneous excitation, and 800-nm pulses to
achieve homogeneous excitation via three-photon absorption.
At the highest fluences, both for 267-nm and 800-nm pump pulses, a degenerate electron-hole plasma (EHP) is generated
with carrier densities of 1025 m-3 or higher. We observed strong amplification of the probe, accompanied by a rapid decay
(~ 1.5 ps) of the charge carriers. Below ~ 1025 m-3, the EHP becomes non-degenerate and the decay much slower.
A dip in the pump-probe signal was observed, caused by ionization of probe exciton-polaritons by the pump. This effect
allows for a measurement of the exciton-polariton dispersion relation and enhanced light-matter interaction in ZnO