Despite the risks, would you play a game with five-dimensional dice?

You can only roll it in 3-dimensions.
A cube would interact with a 2-d world as a square for all intents and purposes. A tesseract would be a cube to us and a square to flatman. Same deal with a hyper tesseract.
A 5-d cube would be a cube that comes pre-loaded with multiple possible quantum wave states, but we'd have no way of changing the active one, so it'd just be a cube.

This is a 3D representation of a 4D dice rolling:
youtube.com/watch?v=vV3SoY5eTRc

I couldn't find a 5D one, but to give some perspective, this is a 4D 3x3x3x3 Rubiks cube:
youtube.com/watch?v=pS6mvBJATLM
And this is a 5D 3x3x3x3x3 Rubiks cube:
youtube.com/watch?v=EOcJmSyBu_U

If you saw this in real life, would you die?

No.
Although maybe...
Who was that guy that stabbed me?

Who four dimensional horse here?

youtube.com/watch?v=MDvlO9q6qWk

No. Might summon pinhead, though.

>I pick up the dice.
>By rotating it, it goes in on itself and vanishes from the 3d plane, to return a moment later as it tumbles, now buried in my wrist, as an agonizing array of seemingly jagged shapes.

That's just a visual representation

You can't perceive how it would actually look, therefore you can't see it.

It would be extremely painful.

You're a big roller.

For you.

Those are representations of those objects rotating in the 4th dimension.
We 3d beings can't move objects into or out of the 3rd dimensional space. We can only interact with a hypercube as if it were a cube.

Depends on the exact interactions, actually. A 3cube can be anything from a point to a line to a triangle to all sorts of quadrilaterals to a 2space. There's a bunch of ways to put a 2space through a 3cube after all.
Same thing goes for a 5cube and a 3space, but with loads more possibilities.

Someone please explain to me what five dimensional dice would be.

an object where to describe the position of all its possible points you need a minimum of five numbers

>no texture perspective correction
fukkin dropped

Only if I was playing in a holographic universe.

Some Egyptian dude

Quantum entanglement is an entirely different subject (basically it's making copies of atomic particles that move the exact same way without delay over vast distances). It's just something people say to sound smart.

A five-dimensional six-sided die can be represented with a d6, a d8, and a d10. Roll the d10 to determine which "face" of the four-dimensional die to reference, and then roll the d8 to determine which d6 to use. Then you can roll the d6.

The irony, of course, is that what you've just claimed to be an explanation of quantum entanglement is almost completely wrong.

t. grad student working in quantum information science

submerge the situation in R^5

how exactly *does* quantum entanglement work?

Explain like we're stupid cause we are

In a nutshell, if some set of things are entangled, a property that they share is correlated between the two of them.*

For example, you can send a laser into a special type of crystal and get two beams that entangled through a property known as polarization; let's say one beam ends up with polarization 'A' and the other 'B'. Now, we don't know which photon is A and which is B. If you measure the polarization of one of the photons and find that it's B, you also know which polarization the other photon is A using the knowledge you have that that crystal always creates pairs of photons with opposite polarizations A and B.

Entanglement is all about knowing how properties between the entangled systems relate to one another, even if you don't know the 'value' of that property. This is also why entanglement is often fragile; if something else bangs into your entangled systems and interacts with that property without you knowing, you've "lost" the information you had before and your entanglement is broken.

* Entanglement need not only be of one property, or only with two things. You can entangle more properties with more things if you're careful and clever enough.

Two particles share a state despite their distance.

One particle rotates faster, the other will at the same time. Theoretically, this can achieve FTL communication.

Spooky action at a distance, yo.

Sorry to continue to be the quantum poopy-pants in this thread, but theoretically it is well understood that this cannot achieve FTL communication.

The speed of information is real, yo.

Why not? Unless you're including the time it would take to get one side of the entanglement to where the information needs to get.

If the particles react to one another instantly ignoring space, I don't see why it couldn't lead to FTL communication.

But then again, I'm just working through this logically. And I well know that these kind of topics don't work if you apply standard logic.

I use a virtual dice roller.

All my dice can be n-dimensional without an issue.

No you're not.

Oh, but you can use standard logic! It's just a matter of being clear about what assumptions you have to work from.

Let's take the example that everyone loves to use. You and I have found a way to entangle the property of spin between two atoms. When one is up, the other must be down. Now, after we do a great job entangling them, we put them in boxes and make sure they don't interact with anything while we speed off across the cosmos.

Now, let's say you want to communicate with your friend. How do you do this? Well, you measure the spin of your particle in a box and find that it's down. You now know that, if I were to look at my atom and measure the same thing, I'd find it pointing up. Yet, we haven't really "communicated" anything, have we? We already knew that one must be up and one must be down at the onset.

So you say, 'Hey! If I measure my spin like this, it's guaranteed to be up, but if I measure it like this, it'll be down. And because our particles are entangled, this'll force your atom to be the opposite when you measure yours.' So you pick your measurement to give the desired result, and force me to get a 'down' when I measure my spin. Great! We've communicated, right?

There's a problem; I don't know how I should measure my spin. I can't interpret the correlation if I don't measure the same way you do, so somehow you have to tell me how you measured it. And there's the rub; you need a way to get new information to me about your measurement if I am to use the correlation to extract information from the spin of my particle.

So you call me up on your space-phone to tell me about what you did with your particle-in-a-box-a-phone, after which I pitch the useless thing away because we've been forced to respect the speed of information.

Assuming we are entangling one atom only, then we still could communicate easily. Morris Code works wonders. Fast spin verses slower spin can pass for dots and dashes as long as the speeds are relative to each other.

But wouldn't a true Quantum Communication Device have more than a single atom entangled with each other to prevent this kind of thing from being an issue?

I actually am a bit sorry; I'm a pedant because I think it's important that people realize quantum mechanics isn't all that crazy and weird, not because I like killing people's fun. A lot of shit gets handwaved because of 'quantum weirdness' from biology to philosophy that simple doesn't stand up to any rigor. I've wasted a good part of my life trying to understand it, so I figure I might as well do my best to help others.

'Spin' is not really a 'spin' like a top; it's best to think about it just as an internal property that can take certain values. Hell, we could have called it 'color' and labeled them 'red,' 'blue,' 'green,' etc, and we would still have the same problem: namely that if you wanted to do something to change what I measured on my end, we'd need to share some other information to make sense of the correlation.

This is why just entangling more atoms and using them doesn't quite work. So we have a set of measurements with one pair that we use to communicate and another to try and send that precious information we need to interpret the results. How do we know how to measure this second pair though? Well, that's easy! Use a third pair. But how do we know how to measure the third pair?

Sadly, we're left with pairs all the way down.

Why can't we then set a meaning to certain spins / colors / what have you before we separate the Entangled Atoms?

It doesn't necessarily sound like a physics issue, more like an organizational one.

Man, this line of reasoning is actually doing wonders for my coke hangover.

Ah!

But see, then we've already shared the relevant information before we even bothered measuring the damn things. If we just agree on everything beforehand and then check later on, we can't "communicate" anything new. We're just confirming what we already knew.

If you want to tell me something new that we didn't agree on, you have to do something at your end to change something at my end - the most rudimentary picture of communicating. And for me to realize you've actually changed something on your end to effect what I see on my end, you don't have to tell me what you saw, but I do need to know what you did.

It's an issue that cuts right to the core of physics; information. Either you already have all the information you needed to begin with (making it pointless), or you need more information to understand what you've seen (making it worthless).

>We're just confirming what we already knew.
Not what I meant.

If we set a list of spins and their corresponding letters or meanings we could transmit new information. Such as news, discoveries, porn, quantum fetishes, whatever through the entangled particles without having agreed on it before hand.

Its similar to a knock code from WWII. The same twenty-five knock series can be combined to transmit anything from jokes through escape plans.

KNOCK KNOCK

WHO'S THERE

EM Drive

It may or may not take a long ass time but that sounds like it could be used to make binary code.

If your atom is down that means 1. If it's up that means 0. 01101001110000101010101.........

1/2

The 'knock code' is reliant on two things; the first, that you now how to interpret each set of knocks. This is easy enough, and we can agree to do this ahead of time.

Second, we need to agree on how I am to 'measure' your knock code. Fortunately, this isn't really ever a problem. Everyone would know that to 'measure' your code in real life, to get information from it, they choose to listen and keep track of silences versus knocks. As the communicator, you get to choose how those silences and knocks get across, so there's really no problem in not telling me ahead of time what message you're sending. I know how to receive it, and you have direct control over how those silences and knocks stack up to one another through the air - you're literally sending me the 'spins' in our quantum case.

Interpreting 'silences and knocks' is not as easy with entangled properties of quantum systems. How you check the spins is as important to what spin you find as how the spins were entangled. To stretch the analogy a bit, it's as if which ear I listened with made me hear something else. Say I listen with my left ear, I could hear 'knock knock silence knock,' but if I listen with my right I'd hear 'silence silence knock knock.' Now, these mean two different things, and I have to know which ear (read: which measurement) to use. With classical information like these sounds, we could agree that I always use my right ear, and thus we avoid the issue entirely.

The issue is that you can't know if the particle's state has been determined, IE if a message has been sent, without measuring the particle's state.
And once you measure the particle's state, you open the magic box and the fairy flies away.
And you don't know if a message has been sent until you open the box and see HOLY SHIT THEY'RE ALL UPSPIN WAR WAS DECLARED. But if you open the box before that you just get gibberish and you've broken the space magic.

2/2

What about the quantum case? Let's establish a "knock code" with two spins, where Up - Up means one thing, Up - Down means another, and so on.

A breakdown of every way you can try to use them to communicate with me:

1 - You entangle the pairs, measure one so that you know which is which, then send me the atoms that have the right code, like you would send the knocks and silences through the air. PROBLEM: you have to physically send me the atoms, and this can only be done at (fastest) almost the speed of light.

2 - You entangle the pairs, then split them up. We both agree to measure them the same ('Lets both use our right ears!) beforehand, and then we find opposite codewords PROBLEM: as we've already hit home a few times, we've learned nothing knew, just that the spins in my box were one way and yours the other.

3 - You entangle the pairs, then we split up. You want want to change what direction the spins are in my box to be the desired codeword. PROBLEM: any means you would have of directly changing my spins would be matter or energetic, forced to respect the speed limit.

4 - You entangle the pairs, then split them up. Now you want to change what codeword I have in my box. You can't touch my atoms (3) - I'm a galaxy away - but you know that they're entangled. Because of entanglement, you know that if you measure, say, Up - Up, I _must_ measure Down - Down if I look at it the same way (listen with the same ear, for example). So you cook up a measurement that guarantees you measure Up - Up, forcing my codebox to be Down - Down after you've finished your work.

PROBLEM: you are relying on the fact that you can _choose_ how to measure to influence the outcome after we split. If I don't know your choice, I can't guarantee I'll measure it the same way to see the desired result. I could take a random guess and hope it's right, but if I get 'Down - Up,' I will never know if I made the right guess until we have another means to communicate the choice you made.

3/2

Communicating via entanglement relies on your choice of measurement super far away impacting my measurement, but we need to both be operating on the same page to get the desired message. This is why no amount of code nor pairs of atoms will get you the desired result if you don't also send some information in a "classical" way (via light, electricity, etc).

You need a way to communicate how you measured that a.) we can both interpret and b.) does not rely on our measurement choice to change the outcome.

There's no way to measure the particle without altering the entangled trait had it already been set by the other party?

Again, it is sounding like an organizational problem more than a physics one. If you can have a hard set of rules on how to interpret the different spins you can transmit new information.

You would have to do the prep work before hand, setting up the system and ensuring its efficacy on Earth with traditional communication methods to ensure accuracy.

Ah! Maybe this is the confusion that I just haven't been seeing. Once one of you has measured your spin, that's it. The games over. By measuring, you've broken the link, and from that point on they are two separate atoms. They are no longer entangled. If I measure and then do something to my atom, it no longer correlates to the behavior of yours.

There are definitely ways to measure one particle that won't result in you interacting with the entangled property, but the hope of using entanglement for FTL communication is that by choosing that measurement you could 'send a message' by influencing the entangled property on the other end before your buddy does their measurement.

Let me turn the tables around; describe to me a setup wherein you could use entanglement to communicate new information to me, and I'll try to point out the step that you take to reach that conclusion that is causing the error and confusion.

OK, so attempted applications time. Lemme know what I'm fucking up and why my idea doesn't work.

We entangle 9600 atoms. We put each pair in a pair of boxes. We number the boxes from 1 to 1200 (four pairs of each number). On pair of each number we write one the following: "War with Canada", "War with Monkeys", "War with the Sun", "No War" such that for each number we have one pair of boxes with each message. You take one half of each pair, I take the other. We pray we didn't mix any boxes up.

We agree on a state (on your side) that corresponds to "HAPPENING". and another that corresponds to "Not happening". You hook a clock to a computer and blast off into space.

Every month, I measure a set of boxes, starting with 1 and working my way up. I set the state of the "No War" box 1 to "HAPPENING" and the other three box 1s to "Not happening". Your clock dings saying that a month has passed mytime. You check your box 1s. You see I have told you there is no war. We repeat this every month for a hundred years then run out of boxes.

Pardon, we entangle the 9600 atoms in pairs, not all to each other.

That'd be great, except that you can't reach in and change the state of the first spin to '1' and the others to '0' and maintain entanglement. Implied in that is the idea that you know what you need to do to set each atom to the desired state, which means you must have measured whether or not each spin was in the correct place in your system beforehand.

This breaks entanglement and leaves me blowing in the (galactic) wind.

OK, then I must have misunderstood what you meant when you posted
>So you say, 'Hey! If I measure my spin like this, it's guaranteed to be up, but if I measure it like this, it'll be down. And because our particles are entangled, this'll force your atom to be the opposite when you measure yours.' So you pick your measurement to give the desired result, and force me to get a 'down' when I measure my spin. Great! We've communicated, right?

Ah! Yeah, the idea is that the choice of how we measure changes what result we see. Perhaps I should have been a bit more explicit in stating

>And because our particles are entangled, this'll force your atom to be the opposite when you measure yours _in the same way_.'

Sounds like all you need is a way to measure if it's 'spinning' without opening the box.

Is it simply impossible to put some kind of sensor into the box and never open it?

I mean hey maybe it is, but I don't know.

If it is, is this a technology gap or seem to just be a rule of the universe?

So, to summarize:
If I measure with method A and then you measure with method A, you will observe state 0.
If I measure with method B and then you measure with method B, you will observe state 1.
If we don't measure with the same method, you will observe a state independent of my measurement method.

Is that correct?

Oh, you can't agree on a measurement schema beforehand because you set the bits by measuring them.

Sadly, it is simply impossible. Put another way, how can we get confirmation of how something is 'spinning'? Well, something _must_ interact with it. The thing that interacted then changes based on how the object was spinning and look at that change to learn about the 'spin.'

This is the essence of the whole divide between classical and quantum 'systems.' A classical system is large enough that this interaction pales in comparison; it basically has no discernible effect. We can throw light at a baseball, see it reflect off, and always know 'where' it is by measuring it with light. A quantum system is small enough that the interaction of measurement changes it. We can throw light at an atom and collect the light to get the information we desired, but in doing so the atom-light interact has changed the atom.

It's this idea that's encapsulated by Heisenberg uncertainty; there is a _hard limit_ to how much we can 'know' about a system at any moment. In extracting information about one thing we lose track of what's happening to another.

Close. Remember, we don't 'know' ahead of time which of us got the '0' or the '1' for a given measurement, only that our answers to the same measurement setting will be the opposite of the other.*

* I'm going to bury a technicality here - if we don't measure with the same method, our measurements can still be correlated, but we need multiple copies AND a list of each measurement setting to tell if they were truly correlated.

Precisely!

>Close. Remember, we don't 'know' ahead of time which of us got the '0' or the '1' for a given measurement, only that our answers to the same measurement setting will be the opposite of the other.*
That makes sense, and indeed kills FTL communication dead. Thanks.

I've heard some mumbo jumbo about jamming proof quantum radar that supposedly uses entanglement and SUPPOSEDLY China has """working""", you know anything about that shit?

Does the spinning cause any kind of reaction to it's surroundings that can be detected? You don't measure if the atom is spinning, you simply detect when the 'air' around it is 'humming' which indicates the atom is spinning?

It's not actual, physical spinning like that. Spin is a property of particles that can be 0, 1/2, 1, 1 1/2, 2, etc.

A bit, yeah.

IIRC, they actually rely on polarization entanglement and use the same tricks that people want to use in quantum communication.

Jamming relies on 'spoofing' the signal; with regular radar, you try to confuse the source by sending out your own signal to fake it out or make it impossible to process what it receives.

Basically, what you do is you throw a bunch of your polarized particles (photons, for example) at something and see what comes back to tell if it's hit anything. The problem is that, to get an accurate measurement of the polarization, you need to choose which 'direction' to measure it. If you're tricky about the initial polarization of the stuff your throwing at the plane, even if they can measure it as best as possible, when they try to spoof and send something back to you, you can use the statistics of the signal you receive to tell 100% if someone is messing with you.

It doesn't mean that you always get what you want, but it does mean you can always tell when someone's messing with your shit. Just like quantum communication. As far as how far along it is / if it's actually a practical technology - that's anyone's guess. Most of the people I've heard talk about similar applications call it 'cute,' so take that as you will.

As I mentioned above, take the label 'spin' with a grain of salt; it's better thought of as some isolated internal property. Now, spin _does_ interact with things (namely, magnetic fields and angular momentum). If you see a change in those, that means the field / moment has also interacted with the spin. Sadly, and we're left in the same situation.

Even in your example though, how does the 'air' 'hum'? If it's 'humming,' then some part of it must have had some interaction with the spinning object to 'know' it was there spinning.

And with that I have to sign off for the night. Hope I've at least given you some interesting things to consider if not also a bit better of a grasp on what entanglement is and what you can do with it.

Thanks for being interested fat/tg/uys.

Thanks for putting your knowledge to use making Veeky Forums the best board!

Simply being able to measure if it's 'spinning' would be comparable to an on/off state which is comparable to 0 or 1 which is how computers communicate.

You don't have to see what it's actually doing to see if it's doing something, is simply doing something is enough to change 0 to 1 and when it stops changing 1 to 0. If you can do this predictably you can communicate. You don't have to know how the atom is moving, which direction, ect ect ect. You don't have to tell what changed, just that something changed. Of course this would require that the change you are detecting is only possible if the entangled particle also changed and for all I know that's just No. Meh, this make my head hurt.

Does the magnetic field also destroy the entanglement?

Absolutely any method of telling what the fuck a particle is doing alters what the particle is doing and destroys entanglement.

;_;

It changes how the particle behaves in an external magnetic field. So to measure it you poke your particle, see what it does, then slap on a strong magnetic field, poke it again, and see what's different about how it reacts the second time. As you can imagine, the particle has now been thoroughly disturbed.

>you simply detect when the 'air' around it is 'humming' which indicates the atom is spinning?

The "hum" around a spinning object is the result of that object interacting with the air, slowly draining its kinetic energy and thus slowing the spin down. So you're not really measuring it without influencing it, it's just that the air that was already there is now effectively part of your instrumentation.

Normally this loss of rotation to the air around it won't change things very quickly, since the spinning object is most likely far more massive than the air around it. But when dealing with quantum mechanics the shit we're looking at is so tiny that anything whatsoever we do to poke them will have a large impact on it.

Sorry user to be another party pooper
en.wikipedia.org/wiki/No-communication_theorem

I think I get what you're saying. It does seem a tricky issue, but also what that seems like something someone will eventually find a cheataround.

...

This thread is fun.

How do you know they're ever entangled then?

A three-dimensional gaming area couldn't even contain a five-dimensional shape. We could see a tiny three-dimensional cross-section of it (or rather, a two-dimensional image of a three-dimensional cross-section of it) but we couldn't see what face was showing. And that's assuming it doesn't crush the gaming table instantly as a three-dimensional object would when passing through a two-dimensional membrane.

Maybe some of your d6s are actually tesseracts and you just never noticed.

>this thread
My brain hurts.

Wouldn't it have infinite mass, though? Or at least a much higher mass than a die that only exists in three dimensions?

The amount of "stuff" in a 5d object can be found by integration just the same as one in a 3d object. Gimme a density equation and boundary inequalities and I can tell you how much mass is in any arbitrary 5d object.
It'd certainly have MORE stuff in it, but wouldn't have world-ending mass.

As I see it, there's two possibilities.
We're all already 5d but don't do shit with those extra two ds, like very fancy tokens that have wonderful artistic curves in X and Y but are just a flat 1mm thick in Z. In this case it'd have extra mass that would seem to come from nowhere, but it'd still be finite.
Or the 5d object has 5d mass but can only project whatever portion of that 5d mass that corresponded to the portion of it that was in our 3space. In this case, all behaves as normal except that its mass will change as much as its shape does as it passes through our 3space.

If it did have infinite mass, it'd just straight-up annihilate reality inside its forwards lightcone.

I always thought the SF writer John C Wright explained it well. One of his main characters is a 4th dimensional girl. He says that if you pretend 3-space is a piece of paper, a 4-space shape is like a squishy ball placed on that paper. If you rotate it one way, it's a sphere to the residents of Flatland, if you rotate it another it looks like a cube. It still has finite mass, it is just "deeper" than we can imagine because we don't have a perceptual set equipped to intuitively measure "depth" as 2-D people.

Although our real universe has so many more issues than just rotation and geometric shape that influences what happens when extra dimensional crap sticks its finger in 3-space.

Well, that's why you have a lot of redundancy.

Is there any reason to assume that extradimensional crap even exists?

Density is mass divided by volume, and volume is only three-dimensional. A 4d object contains infinitely many 3d cross-sections, each of which has a finite mass and volume.

Which is why you'd have to give me a 5d density equation. Instead of m(x,y,z) you'd be giving me m(v,w,x,y,z).

Lots and lots and lots of math involving string theory, if I understand it right. I am a very amateur physicist and only know slightly more than a completely ignorant person. I have a friend at Texas A+M who is a grad student in physics and his specialty is stuff like this and I love asking him stuff about it.

>lose all the dice because they keep rolling away in time

>You can entangle more properties with more things if you're careful and clever enough.
What if we just took a bunch of nothing, rigged it to explode so hard it realitized and then left it for a dozen billions years?

A 3d object has infinitely many 2d cross sections

However, each of these planes has no depth, and therefore each plane has no volume (x,y,0) and as such no mass.

gradfag from earlier plz tell me how i'm wrong

Wow, I learned a lot from this thread. Thanks grad student user!

/thread

If the EmDrive really is pushing against the quantum vacuum, shouldn't that imply that 1) the basic "we know how QM works" assumption of the theorem is wrong and 2) some sort of non-local pilot wave model is more accurate?

This is why reasonable people use Astropaths.

youtube.com/watch?v=jCAqDA8IfR4

everytime I feel like I understand 4D, I don't.
At first I thought it was time.
Then I thought that it was just 2 extra directions to move in that we don't have.
Then I see all the shit like with the horse becoming the entre world at certain angles and I realize that I have no idea what I'm actually looking at.

When you look at it from a math perspective it all becomes trivial.
Go back to school.
Take math classes.
Bug your professors during office hours.
Get educated.
Ruin cheap SF for yourself.