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/sci/ - Science & Math

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File: 17 KB, 300x309, Fig_37-3_Two_Slit_Experiment.jpg [View same] [iqdb] [saucenao] [google]
5671777 No.5671777 [Reply] [Original]

>>fuck >>this >>shit.

aren't you guys fed up with quantum bullshit by now?

>> No.5671791

Yep

>> No.5671794

>fed up with the way nature works
I'm not sure I understand what you're saying, OP.

>> No.5671796
File: 147 KB, 1280x960, 45645634635.jpg [View same] [iqdb] [saucenao] [google]
5671796

You have to understand that choice is a fact before the two split thingy becomes obvious.

>> No.5671800

>>5671796
If "choice is a fact" why can't all the balls choose to just make two lines on the back wall?
>its not a matter of choice, its a matter of interference

>> No.5671812

>>5671800
Because that wouldn't allow them to express themselves. These particles identify as waves.

>> No.5671820

>>5671812
they aren't expressing themselves, they are bound by the physics of being particles identifying as waves and will do the same thing on average every time because they have no choice in the matter

>> No.5671842
File: 238 KB, 1550x1137, Double slit bullshit.jpg [View same] [iqdb] [saucenao] [google]
5671842

Obligatory

>> No.5671854

>>5671842

what?

>> No.5671864

>>5671842
haha. fucking saved

>> No.5671863

this is so exciting

>> No.5672328

>>5671842
Single slit diffraction, look it up

>> No.5672332

>>5671820

Stop trying to repress them.

>> No.5672333

>>5671842
why hasn't anyone considered that the second beam of light maybe interfering with each other?

the single beam is different because it doesn't have another light influencing it

>> No.5672336

>>5672333
http://www.math.ubc.ca/~cass/courses/m309-03a/m309-projects/krzak/

>> No.5672337

>>5671777

Just turn your computer off and walk away.
Just walk away.
We'll let you live.
Just walk away.

>> No.5672505

so are waves particles or not?

>> No.5672507

im guessing maybe this is a problem of scale?

>> No.5672510

>>5671842
But you do get that with a single slit.

>> No.5672535

"quantum" is at the same level of buzzword faggotry as "democracy" and "freedom"

>> No.5672737

>>5672535
Perhaps in popular parlance.

>> No.5672749

>>5671842

You get the particle pattern with the single slit.

>> No.5672751

>>5672535
The fuck did you just say about muh freedom?

>> No.5672754

>>5672510
>>5672749
Have you ever done the experiment? Look up what single slit diffraction is. Also, get a laser pointer and do the double slit experiment for yourself.

>> No.5672757

Best way to describe a particle at a moment in time is as a unit vector (A). The projection squared of this vector onto another unit vector (B) is related to the probability that the particle A will be measured in state B.

>> No.5672758

>>5672754

Yeah, you're right.

>> No.5672768
File: 157 KB, 340x444, 133.jpg [View same] [iqdb] [saucenao] [google]
5672768

>>5671777
Quantum physics is way overrated. Now it's a buzzword in popular culture. I can't here any more about about double slit experiment, wave/particles, wave function and especially Schrödinger. Tons of idiotic jokes about him. The next only a little less irritating things would be black holes, aliens, time travel and multiverse.

>> No.5672772

>>5672768
hear*

>> No.5672773

>>5672337
uuuh... I'm sorry?

>> No.5672774

>>5672768

Most people only understand the dumbed down history channel version of quantum mechanics.


The real Quantum Mechanics is math, and lots of it. The interpretations of that math is what you hear about.

>> No.5672792

>>5672768
Atomism physics is way overrated. Now it's a buzzword in popular culture. I can't hear any more about about reduction experiments, atom/void, atomic collisions and especially Leucippus. Tons of idiotic jokes about him. The next only a little less irritating things would be Chthon, nymphs, Aether travel and Olympus.

>> No.5672798

The interference disappears because the photons used to observe the particles collide with them and change their destinations.

The More you Know...

>> No.5672799

>>5672774
Not to mention that theoretical physicists can literally postulate almost anything and as long as they can then come up with some equation to fit their own theory it can be taken as legitimate work. Borderline solipsism.

>> No.5672807

There seems to be some confusion on how this experiment works. Is it done with photons or electrons? And would it make any difference?

>> No.5672812

>>5672807
It's a lot easier to do with photons, and that's how it's usually done. But it can and has been done with electrons, and even large molecules such as fullerenes.

>> No.5672813

>>5672807
It can be done with any particle subject to quantum phenomena. So pretty much anything subatomic.

>> No.5672819

>>5672798

I thought it was the measurement itself that changed it. Not just the interference with photons?

>> No.5672831

>>5672798
so don't use photons....use electrons... or fullerenes..... or marbles

>> No.5672835

>>5672831

if you use marbles, you get 2 lines corresponding with the size of the slits.

if you use atoms,electrons, photons, or even bucky balls you get the interference patters. If you shoot 1 photon/electron/bucky ball at a time through the slits you still get the interference patterns.

>> No.5672836

>>5672798
This is not quite true. For example, I can shine a light only on the left slit, and get no flash at all for half the electrons. But there's still no interference pattern, even if I only count the electrons that didn't cause a flash (i.e., the electrons that scattered no photon, because they went through the right slit.) It's the entanglement between electron and photon states that destroys the interference pattern, and this entanglement can be created by shining light at just one slit.

>> No.5672845
File: 51 KB, 334x500, Vladimir_Putin_in_Jordan_13_February_2007-18.jpg [View same] [iqdb] [saucenao] [google]
5672845

cymatics, everything is a liquid

>> No.5672859

>>5672819
Observation inevitably interferes with the system.

>> No.5672860

>>5672835
I think if the length between the slits and the screen is large enough you see an interference pattern. But that length needs to be whopperish.

>> No.5672862

>>5672859

No dude, it's measurement.

>> No.5672891

>>5672836
I don't think it's right to say that just because you got a null result from your measurement device that it didn't interact with the system. Consider a device like yours that only registers if a particle is in a certain region. I prepare a particle with a given momentum. I then measure it with your device, and the result is null -- the particle is not in the given region. If I remeasure the momentum of the particle, there is a good chance that I will find that it has changed. Clearly there was momentum transfer between your device and the particle.

>> No.5672908

>>5672862
same shit

>> No.5672921

>>5672908

In the Double Slit experiment, when they observed the photons that went through each slit but didn't save the data. The result was a diffraction pattern. When they were collecting data, they found a particle pattern.

>> No.5672927

>>5672921

are you fucking retarded? please leave. read up on the quantum eraser before you humiliate yourself further.

>> No.5672934

>>5672891
Oh, I agree, there is an interaction with the system. But what happens is that the particle goes into a superposition state. Let's say your device measures if a particle is on the left. The initial state is |left> + |right>, which is a (simplified) zero momentum state. The final state is |left,click>+|right,no click>. But we're now in a position basis. We can rewrite this as [(|left>+|right>)+(|left>-|right>)]|click> - [(|left>-right>)-(|left>+|right>)]|no click>. If we confine ourselves to either the click or no click branch, we have a possibility of getting a nonzero momentum (|left>-right>). In our original state, the two (|left>-right>) bits cancelled destructively, but now that we're entangled, they can no longer cancel. But there's only one part of the state where the particle collided with the device--the click part. I guess you could say that not colliding and colliding are both "interacting" but I feel like that hides the important facts: namely that a mixture of "non-collisions" and "collisions" can kill coherence, so long as you form an entanglement by the process as a whole.

>> No.5672944

i hate all of you so much

>> No.5672942

>>5672921
One of the reasons it's hard to get interference patterns with large, hot molecules is because as they travel between the slits and the target they can spontaneously emit thermal photons. This emission creates a pattern of radiation that could, in principle, be used to determine the particle's position. No one ever collects them to do the measurement; the photons fly off to infinity or hit the walls of the chamber. But the interference pattern is destroyed nonetheless.

>> No.5672971
File: 28 KB, 604x453, fjdkl;jkl;dfjakl;.jpg [View same] [iqdb] [saucenao] [google]
5672971

Just had a thought about the double slit experiment. They had optical sensors to measure photons entering the slits. When they had the optical sensors turned on and recorded the results, it showed a pattern you would expect from a particle. When they had the optical sensor tuned on but didn't record the data (like sensor turned on but didn't have it hooked up to a disk or magnetic tape drive to record) it showed a pattern that you would expect from a wave. They concluded that that it was pure probability until it was consciously observed at which point it collapsed the wave function and displayed the particle pattern. Consciousness observation changed the outcome of the experiment.

My thought, or question rather, is what happens when they leave the optical sensors on, measure the data, but don't look at the data. Like burn the date or something. Now the 2nd part of this. If it doesn't collapse the wave form and it shows a wave pattern. Can you then show the data, while not directly observing it yourself, to an animal of some kind. What would happen then? Because if the wave/particle pattern is determined by conscious observation, then having like a monkey observe the data would be an accurate test of weather or not animals possess consciousness.

tl;dr Can you use the double slit experiment to test life forms for consciousness?

>> No.5672975

>>5672971
Very funny. You know damn well that that's not how the double slit experiment was done. The experiment is confusing enough to people without describing it wrong.

>> No.5672993

>>5672934
To clarify the point I was making: in the double slit, if you shine light on the left that's barely a high enough frequency to differentiate left from right, you get the classical pattern. If, on the other hand, you shine crazy high-energy gamma rays on the left side, you'll get a pattern that looks like the right side classical pattern plus a huge, wide spread out left side pattern (because of the huge momentum kick). The size of the kick you give on the left does not affect the pattern from the electrons going through the right, except insofar as it kills the interference pattern with the left path. Once your frequency gets high enough to totally kill the pattern, you can turn up the frequency as high as you want, but the pattern from the right slit will no longer change.

>> No.5673083

>>5672934
I don't think we disagree on any facts. Presuming that by "non-collision" you aren't implying that there was no momentum transfer between the two objects.

>> No.5673106

>>5673083
Yeah, but see >>5672993. The momentum transfer is almost totally to the "collision" branch. The part that doesn't collide keeps the same momentum, it's just that to divide the state into colliding and non-colliding parts, we must switch bases, and the left/right basis does not have the same eigenstates as the momentum basis, so we fail to conserve particle momentum. But if your device gives a huge kick (larger than demanded by the uncertainty principle), the "non-colliding" part of the wavefunction will not care.

>> No.5673128

>>5673106
You don't ever fail to conserve momentum. That momentum came from the measuring device. If you were to measure your device's momentum before and after the measurement (either by a normal strong measurement, in which case you wouldn't know which slit the device was measuring at, or by weak measurement, in which case you could), you would find that the change in momentum of the particle is exactly offset by the change in momentum of the measuring device.

>> No.5673145

>>5672819
The actual act of measurement is what screws things up, bouncing photons onto really small things is bound to change things.

It's not like the system magically knows whether someone is watching it.

>> No.5673164

>>5673145

please read up on the quantum eraser.

if what you say is true than the "erased" eraser should work even less.

>> No.5673181

>>5673128
Sure. That's why I said you don't conserve *particle* momentum.

>> No.5673234

>>5673164
In the quantum eraser experiment, the interference pattern is screwed up whether or not the information is subsequently erased. The difference is that if you measure your measuring device in a way that destroys the which-slit information, you can know how the measuring device screwed up the interference pattern, and you can thus recover it.

For example, one way to do it is to measure the momentum of the measuring device, which tells you how much momentum was transferred to the particle and therefore how much the interference pattern was offset.

>> No.5673251

>>5673128
A point worth making is that there's no way to shine all the light on one slit. That implies the photons have infinite momentum. There will always be some small part of the photon's wavefunction shining on the non-measured slit. Normally we could neglect this, but it's essential to include this part if we want to see why the momentum of the photon is changed by not interacting with the particle.

>> No.5673267

>>5671820
Check your photon privilege

>> No.5673301

>>5673234
It is possible to design an experiment where the interference pattern is first screwed up, then returned, without ever making a measurement (the only measurement is the final one to see the pattern). All you need is a couple of particles and a control-not operation between them.

Let the particles each have states |0> and |1>. Let the initial state of the system be |00>+|10>. You'd get this state by sending the left particle through an appropriate beamsplitter. If you try to interfere the left particle with itself, you'll see an interference pattern. Now, send the pair of particles through the control-not gate, so that the right particle switches states if and only if the left particle's state is |1>. The new state is |00>+|11>. If you send the left particle through a beamsplitter, you will now see *no* interference pattern. The interaction with the right particle has destroyed it. However, if you now send the particles through a second control not gate, you will get out the state |00>+|10> again (or with a minus sign, depending on how you build your gates.) That state will now show an interference pattern if you look at the left particle--it will be the same pattern as you would see if you never had any interactions. Thus, you have the ability to arbitrarily destroy and return interference patterns. Indeed, you can do this even if the left particle starts in an arbitrary state. So long as you send it through an even number of control-not gates with its entangled partner, the interference pattern will return.

>> No.5673381

>>5671777
>Video recording "faster than light"
http://www.youtube.com/watch?feature=player_embedded&v=-fSqFWcb4rE

What would the double slit look like as it happened?

>> No.5673387

What are some good examples other than light, of the slit shit? Other "natural randomness"

>> No.5673392

>>5672807
The experiment is only meaningful when done with electrons. The wave properties of light have been known for fucking centuries now...

>> No.5673396

End quantum.

Observe everything.

>> No.5673407

>>5673396
Observe quantum.

End everything.

>> No.5673435

>>5672807
The experiment has been done with everything from photons and electrons to atoms and molecules. Even very large molecules have been interfered. Only the practical difficulties of precisely controlling macroscopic objects limits our ability to keep scaling up.

>> No.5673468

>>5673435

Sure you can't do it with things like grains of sand right?

>> No.5673469

>>5673392
Why does that make the experiment less meaningful with other particles? What you're saying doesn't make any sense.

>> No.5673477

>>5673469
>making sense

>> No.5673482

I always hear this binary interpretation that an electron can either be a wave or a particle, what happens if an electron wants to identify as a little bit of both?

Check your privilege.

>> No.5673487

>>5673482
They do though.

>> No.5673491

The reason you don't 'see' quantum behavior in the macro world is because the sheer number of observations (therefore equations) eliminate all the degrees of freedom.

>> No.5673493

>>5673468
Well the de Broglie wavelength of a grain of sand going 200 mph is smaller than the effective cross-section of 1 MeV neutrinos. Good luck.

>> No.5673498

>>5673491
There are certain substances that will exhibit macroscopic quantum effects though, like superfluid helium.

>> No.5673496

>>5673493

So when do quantum mechanics give way to classical mechanics?

>> No.5673505

>>5673496
They don't. This is why physics is fucked.

>> No.5673501

>>5672921
>when they observed the photons that went through each slit but didn't save the data
>When they were collecting data, they found a particle pattern.

I lol'd

>> No.5673510

>>5673496
>quantum mechanics give way to classical mechanics

wut

>> No.5673518

>>5673491
nigga plz

http://www.youtube.com/watch?v=Ws6AAhTw7RA

>> No.5673519
File: 218 KB, 1280x1024, micro-states1.jpg [View same] [iqdb] [saucenao] [google]
5673519

>>5673496
W-w-when th-they g-give w-w-way?

>> No.5673524

>>5673496
Quantum mechanical effects are responsible for really small things like electron diffraction, and really large things like the large-scale structure of the universe, the dominance of matter over antimatter, certain types of supernovas, just as traditionally large-scale mechanics such as relativity are also responsible for the structure of the universe but also to the behaviors of certain materials like atoms, where the speed of light happens to form on its own something of a limit on the maximum theoretical size of an atom. There are of course more examples, but this is just what I could think of off the top of my head.

>> No.5673542

>>5673468
The closest being worked on right now are experiments with large biological molecules and with weakly-bound clusters of ~100 or so identical atoms. Grains of sand will be doable one day, it's just a matter of technology, time, and clever experimental design.

>> No.5673552

>>5673496
Classical mechanics is predicted by quantum mechanics, as a limit of the theory on scales such that the relevant length scale times the relevant momentum scale is large compared to hbar. By relevant scales, I basically mean the precision to which they are measured--classical predictions will be be subject to errors on the order dx*dp~hbar.

>> No.5673620
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5673620

Obligatory proof that QM doesn't work

>> No.5673637

>>5673620
Operators with the canonical quantization relation do not have normalizable eigenstates. You've just shown why infinity minus infinity is an indeterminate form.

>> No.5673640

>>5673637
*quantization
commutation

>> No.5673645

If I'm not mistaken, don't we switch from complex numbers to real numbers while working on QM? I can't remember exactly why though.

>> No.5673663

>>5673645
QM uses complex numbers in general, but the eigenvalues of all observable operators are real.

>> No.5673671

>>5673663
Right, that's what I was thinking of. Thanks.

>> No.5673669

>>5671777
there must be a parallel universe, where we dont do this.

>> No.5673703

>>5673669
But it still exists

>> No.5673770

>>5673251
On further consideration, I think this is wrong. Because the probe photon is in a combination of momentum eigenstates, it's possible to transfer momentum to the measured particle by shuffling around the momentum states of the probe particle without actually changing the probe particle wavefunction.

>> No.5673773

>>5672773
There is nothing to see here.
Walk away

>> No.5673823
File: 172 KB, 570x526, Quantum_Mechanics_explains_by_sonic.jpg [View same] [iqdb] [saucenao] [google]
5673823

>> No.5674119
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5674119

>>5672921

>> No.5674126

>>5674119
No it isn't. Them measuring the electrons interfered with them so they became particles.

>> No.5674146

My magnetic bracelet stablilizes the eigenfunctions of my quantum probabilities.

It's all so far away from the math at this point in terms of cultural junk that it's best to forget everything you think you know and dive into the books and the hard-core math if you're genuinely interested.

That youtube video of Feynman dismissing a reporter's question about "why" there's a magnetic force coming from a magnet is a great example of the difference between "explaining" physics versus understanding it.

http://www.youtube.com/watch?v=wMFPe-DwULM

>> No.5674202
File: 204 KB, 300x400, spins both ways.gif [View same] [iqdb] [saucenao] [google]
5674202

>OMG SHE GOES BOTH WAYS
>like a bisexual