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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.
(Score: 1, Interesting) by Anonymous Coward on Saturday September 22 2018, @08:22PM (7 children)
QM is incompatible with GR (discrete vs continuous universes). Also, photons do not experience time according to GR. So from whose perspective are they measuring this time?
(Score: 2) by opinionated_science on Saturday September 22 2018, @08:33PM (1 child)
quite. time is reversible. What prevents practical reversion is entropy. Biology is the triumph of conserving entropy at the expense of energy.
There are probably a large number of undiscovered biology processes that rely upon quantum effects.
The most prominent example I will mention for information, is the charge separation that occurs in your eyes, you are reading this with ;-)
(Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:53PM
Some people are using screen readers... Does charge separation still occur in their eyes?
(Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:37PM (4 children)
externally (to the photon), duh.
how can you get "into" the reference frame of a photon?
the photon is "absorbed" by the electron cloud. the energy perturbs the electrons, until one is perturbed enough to move up to a higher orbit. the new state is not stable, so it "relaxes", and the released energy is as another photon. these transitions all take time, breathtakingly small amounts, but not instantaneous.
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(Score: 0) by Anonymous Coward on Saturday September 22 2018, @08:47PM (2 children)
My point was that there is no reference frame by which to measure time in QM. If you use GR, you need to pick one but now you are assuming two mutually exclusive theories to be correct.
(Score: 0) by Anonymous Coward on Sunday September 23 2018, @04:31AM (1 child)
actually, there is. we cannot "get out of" our reference frame w.r.t photons (or get into theirs). we certainly can imagine doing so, and have maths and all sorts of computer sinulations to try and represent doing so, but we are kind of stuck in our own reference frames.
we can certainly see effects of reference frame differences (Mercury's classical vs relativity-adjusted orbit time, a particular nuclear decay rate (muon decay?) that was funally explained whwn taking relativistic effects into account, etc.) but not photons, unless cerenkov radiation is a form of it...
that being said, what happens "inside" a photon that is locked in a photon trap? does time keep advancing inside it (or is it even relevant...)?
(Score: 0) by Anonymous Coward on Sunday September 23 2018, @12:38PM
All that math and computer simulation you refer to assumes GR is correct... which means assuming QM is incorrect. So basically they can conclude whatever they want since theres a contradiction in the logic.
(Score: 0) by Anonymous Coward on Sunday September 23 2018, @03:08PM
could one also argue that the measured times is the time the electron needs to "absorb" the photon, but once does, jumps instantaneously?
so the measured time is the time the photon needs to convince the electron to wholly interact with it?