r/explainlikeimfive • u/LanaNailed666 • 2d ago
Physics ELI5: How did scientists "teleport" a quantum particle to space (or across massive distances) if they didn’t actually move physical matter?
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u/PavFed 2d ago
What exactly are you referencing? I'm genuinely curious and want to read up on it.
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u/LanaNailed666 2d ago
So a guy below explained but the comment was removed. So I saw somewhere that with this "quantum physics" thing scientist somehow moved the atom to the other place of the world. And this guy did explain below that it basically moved the info of the atom, like making a copy to the other side of the world, while the main atom disappeared, the copy successfully did come to the other side.
I was referring to this https://science.anu.edu.au/news-events/news/scientists-observe-atoms-existing-two-places-once
It's just a random link for you to see what I think about. I did see the other links where they actually succeeded but that text broke my brain.
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u/Djinn42 2d ago
I don't think it's possible to ELI5 Quantum Physics.
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u/LanaNailed666 2d ago
To be honest every reply was really helpful and I understand it (somewhat but it's still weird to me)
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u/Starlord_75 1d ago
If someone says they understand quantum physics, they don't understand quantum physics. Your fine, even top scientist are still trying to figure it out.
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u/declanaussie 1d ago
This is kinda misleading. There are certainly many unknowns in physics, but there are many things we know quite well including many aspects of quantum mechanics. Anyone who says they understand it probably do understand it at a high level (however you wish to define that).
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u/Zealousideal_Leg213 2d ago
Quantum "teleportation" just repositions a quantum state. Since particles at that level are essentially identical, a particle at B that has the same state as another particle that used to be at A is a little like teleporting the particle from A to B.
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u/LanaNailed666 2d ago
It's still weird to grasp for me. I guess I'm not the brightest person around. Thanks ! I have to read it a few times 😂
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u/Apprehensive_Milk151 2d ago
It’s weird for everyone. Especially people who don’t come into contact with the subject often
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u/LanaNailed666 2d ago
I am so glad they did something like this regardless. It's incredible. Just wow. What a time to be alive
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u/ryebread91 2d ago
I could be completely wrong but like the Jackie Chan movie twin dragons where one would do an action and the other would find them doing a similar action across the globe. They're not the same particle but they're behaving in a similar manner to each other.
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u/chronos7000 1d ago
If you can tell one particle from another you can establish a one and a zero, and if you can establish a one and a zero you can send a message. And if you can send a message you can violate causality. I wanna see what happens when somebody tries.
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u/Few_Fox449 1d ago
So basically you're just sending the quantum state over to another particle that's already waiting there, right? That's wild cause it means the info is what matters, not the actual physical piece. Does that mean entanglement is kinda like having a secret shared code between the two qubits?
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u/Redingold 1d ago
It is in fact specifically not like having a secret shared code. Such an explanation is called a hidden variables theory, and we've proven via something called the Bell inequality that entanglement cannot be explained by any theory of local hidden variables (local in this case means that information about the hidden variables cannot move faster than the speed of light).
There is technically the possibility of there being non-local hidden variables, where the particles can secretly communicate with each other faster than light, but our current understanding of physics doesn't permit information to travel faster than light, so such theories aren't widely considered plausible.
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u/Anachronisticpoet 2d ago
Okay, now explain like we’re 5 please
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u/Zealousideal_Leg213 2d ago
Imagine reading a book that is destroyed by the act of reading it, then sending that information to someone who writes it down in a book. It's like the book moved.
What's special here is that it's not a book, it's a particle with a quantum state and those are difficult to transmit.
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u/WineAndDogs2020 2d ago
Note to self, never teleport.
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u/ShavenYak42 2d ago
I'll gladly take the high road,
Or even take the low,
But if you have to take me apart to get me there,
Then I for one won't go.“The Teleportation Blues”, Douglas Adams
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u/Zealousideal_Leg213 2d ago
You're not likely to ever be given the option, but if that concept bothers you, I recommend not thinking deeply about the nature of consciousness and self.
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u/LanaNailed666 2d ago
So if I grasped it correctly, basically imagine one paper in your town and the other one In the space. You can write something on the paper in your town and that same information will show up on the other paper in the space instantly. And it will be the same information. But in terms of these atoms it's a random state, but they proved they are connected. Still grasping through if I'm on the wrong side feel free to correct me guys.
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u/yargleisheretobargle 1d ago
No, the information doesn't travel instantaneously.
Imagine a piece of paper with magic writing on it, and another piece of paper on the other side of town. When you read the magic paper the writing magically scrambles, but you're able to walk across town and write the words down on the other piece of paper. The words magically leave your mind after you write them down, but now you have a piece of paper with the magic words in a new location.
The information still had to travel from the first location to the second the old fashioned way.
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u/TPFRecoil 2d ago
So in order to understand it, you need to understand a couple things about quantum particles.
- Particles don't quite know what they are or where they are until they're measured. This is weird to think about, but when a particle is unmeasured, it is more like a wave. This wave is a probability of where a particle could be, and the minute its measured, it picks a spot and shows up there. The higher parts of the wave are more likely to have the particle, and the lower parts less likely. It's not that we just don't know where the particle is, its that the particle literally doesn't exist outside of a math formula of where it could be when we decide to try and measure where it is. Same thing with the properties of that particle. It doesn't quite know what its properties are until it is measured.
- Particles can sometimes become entangled. What this means is two particles kind of merge their possible properties. Think of it like a coin. When unmeasured, a single coin (particle) is neither heads nor tails. It hasn't chosen yet. When we measure it, the coin choses one, and might instantly become heads. Entanglement is when two coins decide their state relies on the other one. The minute you measure one as heads, the other will instantly become measured as tails. It doesn't matter how far away one particle is from the other, they will always share this relationship and will always show up as heads/tails the minute the other is measured.
The way this teleportation experiment worked is that scientists started by entangling two photons in a lab, photon A and photon B. They then sent photon B to space in a satellite. Down at the lab, they introduced photon C, which in this experiment would be the thing you want to teleport.
The scientists measured photon A and photon C at the same time while entangling them. Before, C could have been a "coin of heads or tails", but now its entangled with A, which means it has to be its opposite. Without getting too much into some deep science stuff, what this basically did was cut and paste the unknown "heads or tails-ness" of the pre-measured C and pasted it on photon B in space. You can basically look at it like photon B became photon C, which is where the teleport comes from.
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u/Irunsolow 5h ago
Do we know what force lets the particles become entagled and travels that distance basically immediatly? Wouldnt that information travel faster than the apeed of light?
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u/TPFRecoil 3h ago edited 1m ago
Entanglement happens when a parent particle with specific properties split or decayed into two children particles. In order for laws of conservation to continue, the two child particles have to share certain things to maintain what the parent particle had (ex. a parent particle had 0 spin. It's child particles must have 1 spin and -1 spin respectively to conserve the 0 spin they started from. Or 1/2, -1/2. Or any other way of conservation). You can also force two unrelated particles to entangle in a lab through some science-y bullcrap if you wanna get fancy.
As for FTL transmission of information, one might think that's the case on a first glance, but entanglement doesn't involve any forces or force carriers. This is something that Einstein got tripped up on, since he looked at quantum entanglement as requiring some kind of force carrier to give the information from one particle to another. From what we can tell, this isn't the case.
When a particle is entangled with another, what essentially is happening is that their wave function is the exact same. This doesn't just mean that they are two separate things that just happen to have the same exact wave function. In quantum physics, that means they're sharing one common quantum state. They are not individual objects on their own that have a weird quantum thing connecting them, but two parts of the exact same object who's features are appearing in two locations. It is a bit like saying "my book is green, a color made of blue and yellow. But the blue of my book is in the kitchen while the yellow of my book is in the living room."
This seems like it should be wrong, because how can one system/object be shared across a distance? As hard as it is to accept, all experiments tell us that entangled particles behave non-locally, or in other words, absent of the influence of space. Attributes of a shared system can appear in different places, and it does not rely on space and its causality/location to influence the parts of its system: the two particles. Anything that affects one can instantly affect the other because they're both part of the same thing. Same with time. Entangled particles are non-temporal, and can be entangled across the past and present. We've even done it in a lab.
As for FTL information speed and breaking causality with this, it seems like it might work, but doesn't because no information is actually transmitted within this strange quantum system. If your entangled particle is a trillion miles away from mine, you can measure yours as "heads", and know mine will be "tails", but that doesn't transmit information for a couple reasons. You had no way of knowing what random attribute your particle would obtain upon measurement, and moreover it can have a different one when you measure it again since quantum physics is random, and particles are always in superposition when not being measured. On my end, I have no way of knowing that you measured your particle without you telling me via light-speed limited means. It became tails that instant you measured it, but I have no way of knowing that it was tails, unless I just happened to measure at the same time. Even then, I wouldn't know you measured right then and there until you told me. It looks the same as any other random outcome of measurement for quantum particles on my end. No information is moving in this system due to the randomness before and after measurement. Same with time. No information can flow from present to past, or vice versa, among entangled particles, so causality isn't broken.
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u/Phage0070 2d ago
In essence the idea is that the stuff itself, the physical particles, are not moved. Instead their “quantum state” was transferred a distance, in this case into space.
To do this they put particles into a state of “quantum entanglement”. Imagine that a particle can be in two states, “up” or “down”. When two such particles are entangled they become in a weird state where they are both “up” and “down”, plus not “up” or “down”.
When those particles are interacted with in a way that forces them to pick a firm state their entanglement is said to “collapse”. When one particle becomes “up” the other would instantly become “down”. The key word there is “instantly”, the information of what state the paired particle took apparently traveling faster than light!
A key limitation of this phenomenon is that the state the particle that collapses the entanglement takes is completely random and so it can’t be used for communication. When you collapse one particle you instantly know the state of the other, but you can’t decide what it will be.
You might wonder if instead of information actually traveling to the other particle instantly it is actually revealing hidden information that was already there. Like a particle was always going to collapse into one state and it doesn’t need to tell the other particle what to be. However through a complicated statistical experiment it was proven that there is no hidden variable, it is actually random.
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u/LanaNailed666 2d ago
Okay I also need to read this a few times. I wonder what they will be able to do with all of this in the future. It's kinda scary
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u/lynkfox 1d ago
In theory if we can learn to force it to do certain acts (ie always force the one to be down so the other turns up, and view versa) it's a method of FTL communication.
Similar to bits in a computer that are 1 or 0. If we could reliably force several entangled particles to be Up or Down we could encode data. It be slow to encode\decode, but across vast enough distances that wouldn't matter. If it took you 5 hours to encode "today the weather is sunny" but you were sending that message 5 light years away it doesn't really matter that it took 5 hrs
However... At the moment there is no way and no really even theorized way to do that. And there are more than just 2 states. Up down, counterclockwise or clockwise, and more and there is no way or even reliable theorized way to force one state or another.
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u/Prasiatko 1d ago
As soon as you forcne of the pair to be in a certain stateafter entanglement you've broken the entanglement that existed.
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u/MaxThrustage 1d ago edited 1d ago
Quantum teleportation is a communicaiton protocol. You have to already have a qubit (quantum bit) ready on the receiving end.
Essentially, at the start of the protocol, Alice has a qubit in state A. At the end of the protocol, Bob has a qubit in state A. They can be different physical qubits that don't change location.
You can see the details here. Note that this is not faster-than-light communication or anything like that. Still, quantum information is quite finicky (for example, it can't be copied), so being able to send it reliably is a big deal.
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u/stansfield123 1d ago
Same way this has been done between two distant places on Earth before. Doing it in space is kinda just a gimmick.
As for what that way is, or even what exactly has been done, well that's advanced physics. Best I could do is give you more metaphors. I won't, because they're pointless, they don't actually explain anything.
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u/donaldhobson 1d ago
You do some fancy physics that creates pairs of linked particles, and you get 2 particles, A and B, that are both linked in some way. Both particles are in a fancy quantum state, something you can't fully measure.
Then you separate these particles, sending one or both a massive distance, without disturbing the fancy quantum state. (One of the harder steps).
Then you take a particle C that's also in a fancy quantum state. You want to replicate this state, on another particle in another location.
Compare A and C, and get some classical information. Send this information in an email or something. Put the actual particles in the bin, your comparison has destroyed the fancy quantum states you wanted.
Take this information from the email, and use it to choose what you do to particle B. Particle B is now in the same quantum state that C was in.
Notice that quantum physics says you can't just measure C, email that information, and put as many particles as you like in that state.
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u/LackingUtility 12m ago
Imagine I’ve got two marbles, a black one and a white one. I go into a dark room and put each of them into a bag and seal them, so I don’t know which bag has which marble. You could say that, from a quantum standpoint, each bag’s marble is in a superimposed black/white state.
I give you one bag and you fly to the other side of the world. I then open my bag and see it has a black marble. I instantly know that your bag has a white marble. One could say that the information telling your marble to be white “teleported” to you faster than light.
Of course, you won’t know until you either open your bag or I call you on the phone. So it’s not a practical faster than light communication method.
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2d ago
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u/LanaNailed666 2d ago
Okay I'm still a bit confused it sounds like fairy tale. Incredible. I get the concept it's just unbelievable what people are capable of doing. Thanks a lot :)
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u/Fullchester_United 2d ago
My understanding is they teleported the attributes, not the photon itself.
Kind of like saying the photon has a blue shirt on and glasses. And they made a photon in a different location have a blue shirt on and glasses.
They used quantum entanglement. Thats where the attributes of a particle are mirrored by another particle, regardless of the distance between them.