What is the physics behind quantum tunneling

Spinalcold

One of my favorite quotes deals with the difficulty in understanding this.

Freeman Dyson: "Thirty-one years ago, Dick Feynman
told me about his "sum-over-histories" version of quantum
mechanics. "The electron does anything it likes", he said, "it goes
in any direction at any speed, forward or backward-in-time,
however it likes, and then you add-up the amplitudes and it gives
you the wave function." I said to him, "Your crazy". But he
wasn't."

*ImaLooser*

Quote by Neandethal00

Can we say the particle tunnel through the barrier instantly or faster than c? We don't know how the particle behind the barrier suddenly appears in front of the barrier? Can it be another phenomena similar to quantum entanglement?

The way I look at it, we have only a vague idea of what the "particle" is doing when we are not observing it. There is no particular reason to believe that it moves ballistically, or that it even traces a continuous path in space. I'm inclined to think that it doesn't.

mfb

Quote by derek101

Drakkith
If it's the particle itself that has the uncertainty then:-
Are you saying that 2 protons in the vacuum of space,have the same chance of tunneling through the barrier,as 2 protons in the middle of the sun?

The interior of the sun is a good vacuum on the scale of nuclei: You just have to consider the two protons and nothing else.

There is a pep process (2 protons and one electron fuse), but that is rare.

Quote by ImaLooser

The way I look at it, we have only a vague idea of what the "particle" is doing when we are not observing it.

We have a good idea what the wavefunction does, however.

derek101

[QUOTE=mfb;4171384]The interior of the sun is a good vacuum on the scale of nuclei: You just have to consider the two protons and nothing else.

so 2 protons in the vacuum of space can fuse,and form helium nuclei?

mfb

They can form deuterium (+positron+neutrino), as they do in the sun.
They need a significant relative velocity to have a reasonable fusion probability.

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derek101	[QUOTE=mfb;4171384]The interior of the sun is a good vacuum on the scale of nuclei: You just have to consider the two protons and nothing else. so 2 protons in the vacuum of space can fuse,and form helium nuclei?

mfb Mentor	They can form deuterium (+positron+neutrino), as they do in the sun. They need a significant relative velocity to have a reasonable fusion probability.