How does the observed version of the double slit get by without math?

[DamonL]

TL;DR Summary

How does the observed version of the double slit experiment get by without supported math?

Send a classical particle into a three dimensional potential well. 0 Probability of it tunneling.

It's a classical trajectory with wobble from uncertainty. It's not a wave, but gets wobble from the quantum field influencing it.

https://farside.ph.utexas.edu/teaching/315/Waveshtml/node95.html

Ψ = 0 outside of the well

A measurement way after the double slit shows the entire life of that particle is known via state. The final panel is the exception because the wave will collapse, what matters is what a wave/particle is while in flight.

Duality in flight is not a thing that happens.

 

[PeroK]

Is there a question here? The title doesn't make a lot of sense.

 

[DamonL]

Whenever looking up math related to the double slit, I only get the unobserved version. I need math that shows a decohered wave trying to tunnel.

 

[Nugatory]

A measurement way after the double slit shows the entire life of that particle is known via state.

It does not. It shows that the particle was detected at a particuar location at a particular moment; more precisely (and more in accord with what the math is saying) a detector at that location triggered at that moment. This tells us absolutely nothing about what was going on elsewhere and earlier.

Duality in flight is not a thing that happens.

Duality is not a thing that happens at all. The notion of wave-particle duality was abandoned around 1930 when the modern formulation of quantum mechanics was developed and is no part of the modern theory. Unfortunately by then it had leaked into the popular imagination and lives on to this day as a sort of urban legend, one of those things that everyone's heard but no one can source reliably.

Whenever looking up math related to the double slit, I only get the unobserved version. I need math that shows a decohered wave trying to tunnel.

That doesn't exist, because the wave doesn't decohere until it interacts with the screen, or more precisely, one of the photosensitive detectors (CCD cell or grain of silver nitrate or whatever) on the screen.

We calculate the probability amplitudes at the screen in a way that is analogous to the way that we would calculate the classical intensity of classical monochromatic light at the screen. The difference is that instead of getting intensities that vary across the screen we get probability amplitudes to which we apply the Born rule to get probabilities that vary across the screen.

 

[DamonL]

You missed the part about the particle being measured after the double slit shows it knew to be physical before it started. The delayed choice quantum eraser shows this also.

Good, I don't need Duality.

Are you trying to say a particle is never physical? only a wave?

 

[PeroK]

Are you trying to say a particle is never physical? only a wave?

It's more like a particle is always a particle, never a wave.

 

[DamonL]

No, it's either a wave or a physical particle. It's possible for a wave to make it from point A to B without being measured before the final screen. That's why it shows fringes. You don't get quantum weirdness events when it's a particle.

 

[PeroK]

No, it's either a wave or a physical particle. It's possible for a wave to make it from point A to B without being measured before the final screen. That's why it shows fringes. You don't get quantum weirdness events when it's a particle.

In modern QM, an electron is a particle (more or less by definition). A stepping stone towards modern QM was the De Broglie matter-wave concept, from the 1920's. You can, of course, predict the double-slit phenomenon using this model. But, when modern QM was consolidated in the 1930's, the wave-particle duality in terms of quantum theory became fully explained without the electron having to "know" which to be.

I have two textbooks on QM. The first, by Griffiths, mentions wave-particle duality once, as a historical footnote. The other, by Sakurai, doesn't mention wave-particle duality at all.

That said, you still find a lot of references to it. Perhaps because the observed phenomena can be described as "particle-like" or "wave-like". These terms do not, however, correspond to different components or fundamental behaviours within the theory of QM.

 

[DamonL]

Right, so never-mind you ever catching an observed particle in superposition or tunneling. There is a clear difference of what the particle is with decoherence. I suspect it is classical when decohered and not even using the wave function. The quantum field is responsible for uncertainty and still has influence on physical particles ..making them wobble.

 

[Nugatory]

Are you trying to say a particle is never physical? only a wave?

Quantum mechanics is a theory about measurement results. It allows us to calculate the probability of various outcomes (in this case, the probability of a detection event happening at various points on the screen) but tells us nothing about what a particle is or what unobserved properties it might have.

Your questions are worded in a way that suggests an unstated assumption, namely that the categories "particle" and "wave" are mutually exclusive and collectively exhaustive and that we can use the concepts to explain quantum phenomena. That's a very natural starting assumption; it's consistent with our classical expectations of how the universe behaves and it's what led physicists to the notion of wave-particle duality when they first encountered quantum phenomena at the turn of the last century, three decades before the modern theory of quantum mechanics was discovered. However, that model finds no support in the math of that modern theory.

So I'm not saying "a particle is never physical" or "only a wave". I am saying that there are things that for historical reasons are called "particles" even though their observed behavior is nothing like the plain English language meaning of the word, and that that behavior is accurately predicted by quantum mechanics. It is also inconsistent with the behavior of anything in our classical experience and the common-sense expectations that we've developed over a lifetime in the classical world.

It's frustrating that we can't explain quantum behavior in a way that matches our classical experience and satisfies our classical sense of what a "good" explanation is like... but we don't make the rules, the universe does, and it doesn't care whether we like them or not.

 

[DamonL]

Quantum waves can tunnel, physical particles can not. Is it somehow more convenient to ignore this?

"measurement results"

And, what I'm saying is measurements done after the fact (hitting the final panel) have no barring on what the particle was in flight.

 

[PeroK]

Quantum waves can tunnel, physical particles can not.

How do you know this?

 

[DamonL]

look at the OP

 

[PeroK]

look at the OP

Are you here to learn more about QM? Or, tell us what's wrong with QM?

Particles can tunnel through a potential barrier. They don't have to obey the laws of classical physics.

In one sense what you are saying is:

I've looked at large objects, made of trillions of particles, and I've observed how they behave and the laws they obey. It's impossible that the particles that make up these larger object can behave any differently. They must obey the same laws and behave in the same way.

That was more or less the stumbling block for 19th century physicists. Eventually experimental evidence forced them to accept the fact that the atom is not a miniature solar system; and that an electron is not a miniature snooker ball.

There's no reason that the electron must obey the laws of classical physics. None whatsoever.

 

[DamonL]

The electron has to be decohered to follow classical physics. There is a quantum/classical boundary.

I should probably add that the quantum field doesn't use time from spacetime. Unobserved quantum waves do not age. This is how it knows if a state was triggered in the particles path before launching it.

"That doesn't exist, because the wave doesn't decohere until it interacts with the screen, or more precisely, one of the photosensitive detectors (CCD cell or grain of silver nitrate or whatever) on the screen. "

I'm not good with this answer and I commented why.

 

[PeterDonis]

It's a classical trajectory with wobble from uncertainty.

You missed the part about the particle being measured after the double slit shows it knew to be physical before it started. The delayed choice quantum eraser shows this also.

it's either a wave or a physical particle. It's possible for a wave to make it from point A to B without being measured before the final screen. That's why it shows fringes. You don't get quantum weirdness events when it's a particle.

There is a clear difference of what the particle is with decoherence. I suspect it is classical when decohered and not even using the wave function.

The electron has to be decohered to follow classical physics. There is a quantum/classical boundary.

I should probably add that the quantum field doesn't use time from spacetime.

I'm not good with this answer and I commented why.

What your comments make clear is that you are not here to learn. You think you already know how quantum physics works, so you keep rejecting everything anyone tells you. But you don't actually know how quantum physics works, as all of your comments quoted above show, so this discussion is going nowhere.

Thread closed.