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Bytram (from IRC) writes:

How long does a quantum jump take?

It was one of the crucial experiments in quantum physics: when light falls on certain materials, electrons are released from the surface. Albert Einstein was the first to explain this phenomenon in 1905, when he spoke of "light quanta" -- the smallest units of light that we call photons today.

In tiny fractions of a second, an electron of the material absorbs a photon, "jumps" into another state and leaves the surface. This "photoelectric effect" is so fast that until now it has mostly been regarded as instantaneous -- as a sudden change of state, from one moment to the next. However, new measurement methods are so precise that it has now become possible to observe such a process and to measure its duration precisely. A team from the Vienna University of Technology, together with research groups from Garching, Munich and Berlin, determined the duration of the photoelectric effect at a tungsten surface. The results were published in the journal Nature.

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