#5minphysics 18: Quantum Entanglement vs Faster than Light Communication

Quantum Entanglement is one of the weirdest, and currently perhaps the most technologically exciting aspect of Quantum Mechanics. But even though the measured state of one object instantaneously affects the state of another located across the galaxy, this doesn't allow faster than light communication, alas, as I show in this #5minphysics episode.

[Bazzo]

Simple but one of the most effective explanations of quantum entanglement I have heard - thank you.

[_John_Sean_Walker]

Thank you for the free lecture professor. ☺

[psychepeteschannel]

This is probably impossible, but I have not seen this suggestion in the comments below, so please someone debunk me :D - I set up 3 stations. One in the middle of the galaxy, sending out entagled particles, one partner left, one partner right. On the left side of the galaxy, I measure all electrons I receive, colapsing their wave function. On the right side of the galaxy, they have a double slit experiment set up and since these electrons are already collapsed (due to my measuring in the the left station) they get the "particle pattern". Therefore, if the left station stops measuring, the right station starts receiving an "interference pattern" instead. Alternation between particle and interference patterns creates my 0s and 1s. ...
Now, I assume that entangled particles will never produce an interference pattern or something like that? :/

[mymomentsofzen]

Thank you for yet another fascinating mini lecture. By the way, I love the title "Five Minute Physics". The fact that you can get some of these concepts even close to five minutes, and have people understand them, is downright amazing! I realize that you are just giving us the very basic concepts, and that there is much more to what you are teaching us. Now it is up to us to go out and learn more! Thanks again. I look forward to more next week. PS. I would really love to understand how a black hole can evaporate, and what happens when black holes merge...what is actually merging??

[kamalkatial]

Quantum entanglement explained in a very simple way. Thanks.

[Amridell]

I was first exposed in a serious context to the notion of entanglement in a quantum computing class. We explained entanglement by saying that you can't write an entangled state as a tensor product of pure states, which of course made sense but was rather limited, so I'm really pleased to see an explanation this good and this physical. The question of "what actually happens physically" is not well liked by computer scientists :)

Question though- If two qubits are in a maximally entangled state, applying a gate to one will effect the state of the other. Currently the channel has exactly a 50% chance to flip- Why couldn't we work out a code to set up our qubits in such a state where that level of noise will be lower, and then use an error correcting code to deal with the remaining noise? I think I'm missing something but I'm not sure what. Thank you for the video!

[Elayzee]

This was a ridiculously convoluted way to describe quantum entanglement.

[Zodtheimmortal]

I think that Physicists try very hard to explain away the possibility of breaking general relativity. But how would they react if someone actually invents a device capable Faster than Light Communication? using quantum entanglement in creating ways? For example continuous reading of up and down spin on both particles, and translating to morse code. If you can continuously measure both particles, and force a spin state to a particle, then ftl communication is possible. The particles would need to maintain a state for a period of time, then the instrument would need to force a change of spin on schedule. This could in fact look like a morse code signal. The key is to make the spin detection on the other end look non-random.

[REDPUMPERNICKEL]

In the time it takes to imagine a nanosecond a billion of them have expired.

[naturediary]

Wow! That really is all those things you mentioned, strange, spooky and crazy! Even though had to view this video several times, I still really haven't got my head around this and have a million questions to ask but ah!, that's ok, I was still absolutely enthralled in watching this. So thanks again Lawrence and you have a great weekend too. And btw, you should think yourself lucky you have hair to cut ;-)

[Kawalzki]

So honestly what needs to be developed is the ability to constantly monitor the Quantum state, and the ability to force the "Switch" of the state to the "Direction" that you want, we don't communicate via CB radio by just watching the random radio waves in nature but by harnessing the power and generating the waves so the match the shape and form we want. we can start with the current on off design 1's and 0's of modern computers or evolve to develop quantum state computing introducing multiple dimensions. For read write capabilities.

[hawzhinblanca]

Longer is Better, Please keep going, thanks.

[Alzexza]

Simple and effective.. thank you

I'm not a physicist. So I'm struggling to see what all the hype is about? To over simplify it. It feels like a RSA token. Once the code is set. The numbers look random but they are predictable because of the original predictable source.

My uneducated question is, can you change/influence the spin once they are separated. Does that influence the other spin? That to me would be "spooky", though that's not what im hearing.

[Syncroniq]

Love your videos. They are super "hyggelige" as we say in Denmark.

[jefferygriffith]

It seems like the first thought of all people is to say "who cares about the spin values? if you can check whether a particle is still in a superposition, then that's good enough to communicate a 1 or 0 and then you can string the particle pairs together into a suitable message. i saw elsewhere in one of the rare videos that mention it that the problem with this idea is that you can't TEST whether a particle is still in a superposition without being next to its partner which defeats the purpose of communicating at a distance.

[beelzzebub]

Ok I asked a question about this in the past, but I've refined my example. Consider the following:

I have 2 space stations, A and B - they are 10 light-years apart. A pair of particles has been entangled and are each stored at a space station. I want A to be able to send an instant message to B. I decide in advance of positioning the particles:

1) Station A will observe it's particle (lets say it has an up-spin) and keep that particle under uninterrupted observance.
2) Station B will observe its particle (it will of course be a down-spin due to the entanglement). Station B periodically observes its particle (lets say, every minute) - this will always sown a down-spin as the observation of particle A has not been interrupted.
3) Station A is under attack - to single station B, they STOP observing their particle.
4) Station B continues to observe their particle every minute - as the other particle isn't being observed, the particle at station B could be either up or down (not just locked-in to be down). So eventually, after a few minutes of regular checks, station B records its first ever up-spin. This is the agreed upon signal for "we are under attack".

In my example, information has undoubtable been sent instantaneously (all be it very simple information, but surely an alert counts?) Were any of my premises or assumptions incorrect?

I feel if I get an answer to why my example can't work, I will finally understand this FTL communication issue.

[AsFewFalseThingsAsPossible]

I get that we can't use the actual state to convey information across distance instantly, but since it's time that this arrangement kind of sits in, why not perturb that ? For example, set up an array of quantum states, (qbits ?), and agree here and now that the time between the changing of a particular qbit in the array and another particle in the array has a meaning. Holding the array in place is the tricky part I suspect... If I change the particle positioned at 2, 5, 7, then 0.0001 seconds later the particle positioned at 4, 5, 8 this means "x" whatever this is, could be anything. But if it happens 0.0002 seconds later this means "y". So it is the time between the act of forcing the change that is the information. Thanks so much for the lectures and interacting with your fans.

[adamburt]

Thank you so much, I love your explanation. I'm not even in collage yet and I was able to calculate mass of the sun. I'm so happy😀

[samuelhmullins]

Instead of insincere fault finding what is and is not experiment, I prefer to sincerely ask, "What is and is not INTERACTION considered to be during that experiment?"

Understanding what preserving their state is and is not should help this make sense to me.

[ka-koolkid]

Why do you need to know whether it's a 1 or 0? Can't you just communicate with morse code, meaning who cares of it's a 1 or a 0, as long as you're seeing something, you can count it as a 'pulse'. The number of times you see a 1 or 0 is the number of pulses. Then it's morse code.