[ExI] Quantum Tunneling

[BillK]

On Wed, 20 Mar 2019 at 18:03, Giulio Prisco wrote:
> Very interesting. Open arXiv version of the paper here:
> https://arxiv.org/abs/1707.05445
>
> On Wed, Mar 20, 2019 at 5:33 PM John Clark <johnkclark at gmail.com> wrote:
>>
>> A new upper bound on the time it takes for an electron to get through a barrier by Quantum Tunneling has been found. They found it takes less than 1.8 attoseconds, perhaps 1.8 attoseconds less. They say their experimental results are "in agreement with recent theoretical findings" and "present a compelling argument for instantaneous tunnelling".  One attosecond is to a second as one second is to 32 years.
>>
>> Tunnelling time in atomic hydrogen
>>

But 'instantaneous tunnelling' doesn't mean 'faster than light' as
some news reports claimed.
It's complicated though - explained here:
<https://www.forbes.com/sites/startswithabang/2019/03/21/no-quantum-tunneling-didnt-break-the-speed-of-light-nothing-does/>

Quote:
You might think, based on what you just read about the speed of
quantum tunneling being instantaneous, that this means that particles
can travel infinitely fast, breaking the speed of light, through a
quantum mechanical barrier of finite, non-zero thickness. That's the
misinterpretation that always crops up, and how people fool themselves
(and unscrupulous news organizations try to fool you) into thinking
they're breaking the speed of light.

But all that's happening here is a portion of the quantum particles
found in the pulse tunnels through the barrier, while the majority of
the particles does what tennis balls do: they bounce back, failing to
arrive at the destination. If you can front-load which particles make
it through the barrier, preferentially cutting off the particles in
the back of the pulse, you'll falsely measure a faster-than-light
speed, even though no individual particle actually breaks the speed of
light.
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BillK