Skip to comments.Measuring The Speed Of Quantum Tunneling
Posted on 07/31/2017 8:20:26 PM PDT by MtnClimber
I've been wrapped up in writing a new book, so I didn't notice this right when it was published, but a couple of weeks ago there was a paper in Physical Review Letters titled Experimental Evidence for Quantum Tunneling Time that's worth a mention here. This is, as the title suggests, an investigation of one of the signature weird effects of quantum physics, namely the phenomenon of "tunneling" where a particle encountering a barrier can end up on the other side even though it doesn't have enough energy to get there by normal means. This was followed a few days later by a similar paper taking the opposite side in an ongoing argument about exactly how this stuff works.
Tunneling is, at its heart, a wave phenomenon. Because quantum particles like electrons have wave nature, they can't come to a stop in an infinitely short time, but need to tail off a little more slowly, for basically the same reasons described in this animated explanation of the Uncertainty Principle: If you want a wave-like probability distribution to stop suddenly, you need to add a huge number of wavelengths to get that sharp edge, which means you would lose all information about its momentum. An electron with a reasonably well-known momentum, then, must have some uncertainty in position, which means the wavefunction will extend into regions the particle doesn't have enough energy to reach according to classical physics.......
For a classical particle, the thickness of the barrier makes no difference-- if it can't enter, it can't enter and the probability of finding it in the forbidden region drops immediately to zero.
(Excerpt) Read more at forbes.com ...
An interesting article of new methods to investigate yhe quantum physics of the theory of wave-particle duality.
It's considerably farther outside my comfort zone. Still, an interesting article.
I have worked on circular polarized microwave RF communication systems up to the 30 GHz frequency range. I have never worked on a circular polarized laser.
The lab work in these experiments is getting fairly sophisticated. Experimental physicists are no longer second-class citizens to the theoreticians.
My former colleague Ivar Giaver won the Nobel Prize in 1973 for discovering quantum tunneling. Now he is most famous for his opposition to global warming hysteria.
Great stuff, thanks for posting.
Sounds like a scientific heavyweight...
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