
Double Slits with Single Atoms - bookofjoe
https://physicsworld.com/a/double-slits-with-single-atoms/
======
ridewinter
The phrase "wave-particle duality" obscures the central mystery in quantum
mechanics. You can visualize waves quantized into particles - that's not
mysterious. But how does a single particle create an interference pattern when
there's no other particles for it to interfere with? And how does covering up
one slit destroy the interference pattern when there is only one particle
going though one of the slits in the first place?

Just saying "wave-particle duality explains it" is false. It was a shock for
me to realize that everything taught in physics textbooks was so misleading.
(For a good explanation see MWI)

~~~
ars
MWI doesn't explain much. Why should this electron be able to cross universes
and talk to another one and interfere, while nothing else can cross universes?

Can I setup my experiment so that quantum decay decides if I emit an electron
or not - and then wait for no electron, but I somehow detect the electron that
was released in a another universe?

MWI also doesn't explain why the individual electrons would take different
paths and interfere with each other - the universes are identical, so why are
the electrons taking different paths?

~~~
kanzenryu2
These are exactly the sort of thing MWI precisely explains. It take time to go
through, but this is the best explanation I've ever seen
[https://www.lesswrong.com/posts/apbcLXz5zB7PXfgg2/an-
intuiti...](https://www.lesswrong.com/posts/apbcLXz5zB7PXfgg2/an-intuitive-
explanation-of-quantum-mechanics)

~~~
AgentME
+1, this series of posts is my favorite explanation of it. I love the focus on
it from the philosophy of science angle.

------
akamoonknight
One thing I've wondered recently is how possible it is to recreate the double
slit experiment (with electrons) just in your garage today. It feels like the
cost of the required components have to have come down from whatever it was in
the 60s into if not affordable then at least in the range of a semi dedicated
hobbyist. I will admit to having done very little research in this regard (at
most looking at CRT monitors as potential electron beam sources), but kinda
just intriguing to me what the potential general cycle of scientific
experiment -> commodity might be and how that might vary across experiment
classes.

~~~
jcims
I'm pretty sure Ben Krasnow could pull it off to some degree of satisfaction.
Between his electron microscrope, ion sputtering and mass spectrometer
projects, he probably has close to enough of what he needs right now to pull
something together.

My guess is that he could use his sputtering device or electrochemical
deposition to develop a thin film for the target, electron microscope to mill
and validate the slits in the film, then either the electron microscope
modified or mass spectrometer almost as as-is to actually run the experiment
as long as it's OK to bend the electron's path with a magnetic field after the
slit and scan the interference pattern across a fixed point sensor. The mass
spectrometer seems like it's basically set up to do the atomic interference
patterns already (again assuming steering is OK).

If you're not allowed to manipulate the path of the electron he'd probably
have to come up with a mechanism to detect the interference pattern.

~~~
SAI_Peregrinus
For those who don't know, Ben's Youtube channel is "Applied Science"[1]. All
the described devices have videos on their design/construction/use.

[1]
[https://www.youtube.com/user/bkraz333](https://www.youtube.com/user/bkraz333)

------
laurieg
I'm no physicist but I've always thought about the wave-particle duality like
this:

Image you're tracking someone across the country. You have some data that they
were in 2 towns 100 miles apart with the hour. They must be in a car!

But then, you catch up to them and find their physical tracks. It's a single
line. No car could drive like that. They must be on a bicycle.

You sit there scratching your head wondering how they could possibly be going
by car and bicycle at the same time.

The above situation looks impossible if you don't know about the existence of
motorcycles. I always thought we were dealing with things that were not waves,
not particles but something that shares some of the properties of both.

I'd love anyone with a deeper knowledge of physics to correct me/add to my
thinking.

~~~
RangerScience
Check out the work of Scott Aaronson. I definitely don't understand all of it,
and it's definitely succeeded (I think?) in teaching me quite a lot more about
QM than anything else.

------
notanote
This is a different variation of the double-slit experiment, but it made me
think of this result from last year, which pushes the boundaries of QM effects
steadily further into the classical world.

“2000 atoms in two places at once: A new record in quantum superposition“

[https://phys.org/news/2019-09-atoms-quantum-
superposition.ht...](https://phys.org/news/2019-09-atoms-quantum-
superposition.html)

------
z3t4
Has anyone done a computer simulation of the slit experiment? I predict that
even in a computer simulation with balls/particles, they will create a wave
like pattern due to the balls/particles bouncing. If you take something from
multi dimensional space (3d+time) and project it on a 2d screen it often takes
the wave form.

~~~
kgwgk
Bouncing on what? When you do the experiment and you send a single particle
there is nothing at all between the slits and the screen where the hit is
detected!

~~~
z3t4
My theory is that the balls will not all go in a straight line, some will hit
the slit edge and thus not land straight behind the slit. As with light, the
light will bounce around the room and come though the slit from different
directions.

~~~
kgwgk
That (the interaction with a single slit) would explain difraction but not the
interference pattern (which appears when there are two slits).

~~~
z3t4
Sometimes the ball will go through the other slit. As with light bouncing
around, it will go through both slits.

~~~
kgwgk
But you will have difraction (giving a smooth distribution) when it goes
through one slit and difraction (giving a infinitesimaly displaced smooth
distribution) when it goes through the other. Put them together and you get
more or less the same smooth distribution, not an interference.

------
GlobalFrog
Science-fiction idea: will it ever be possible to test the double-slit
experiment with individual neutrino? There would be multiple issues for that:
the detector, the production of individual neutrinos, the isolation from
perturbations and external neutrinos, the material of the slits... More
seriously, it has been done with individual atoms, photons, individual
electrons, but has this been tested also already with other elementary
particles like gluons, bosons, muons, taus ? And another science-fiction idea:
the double-slit experiment with the Higgs boson, primordial black holes or
quantum monopoles...

~~~
BlueTemplar
Photons and gluons are bosons. Also black holes are in the almost completely
separate theory of relativity, which IIRC doesn't even have "particles" (at
least how they are defined in quantum mechanics...)

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axilmar
Here is a goofy layman explanation:

-particles have variable density and gravity. -particles rotate. -slits create multiple paths. -particle rotation + variable density and gravity makes particles choose multiple paths.

It's an explanation which is totally based on macro observations, as if
particles where balls with a small heavy object in them, thrown out in
multiple tracks. The initial configuration is random, the balls will roll into
specific tracks, but since all outcomes are equally possible, over time the
distribution of the balls will be equal for all tracks.

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goldenkey
See also: actual double slit with huge molecules

[https://www.livescience.com/19268-quantum-double-slit-
experi...](https://www.livescience.com/19268-quantum-double-slit-experiment-
largest-molecules.html)

------
BlueTemplar
Huh, electrons ?? I'm pretty sure that we've been first taught in high school
this duality with photons... (and got told that it worked for any particle
later)

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zevv
I am waiting for the day when we can do this with single frogs.

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axilmar
Question: in the double slit experiment, is the electron gun positioned in the
center of the double slit setup?

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graycat
Okay, maybe I understand and have no question now!

