Ah yes, this helps a lot. Brings back a lot of statphys memories too. Thank you very much.

In a way, a time averaged system could be described as a mixed-state density matrix I suppose, which is where my intuition comes back again. I always picture a single object as being in a pure state, but there are ways it doesn't have to be.

Because when you say that entropy is tied to the probability of an observation, that really doesn't hold for an object in a superposition, since its multiplicity of states is just 1 (the superposition itself), which is where we do need to be careful I guess. I'd call it classical probabilistic, and avoid all confusion with quantum probabilistic.

So, to get more philosophical: It feels like there needs to be some sort of "outside influence" on a single particle for it to have entropy. Would you agree with this line of thinking? For some definition of outside influence.

That is not me trying to say my intuition was right by the way, it wasn't.

Can you point me to specific books or papers (or even terms) that clarify this further, because from my thermodynamics and stat-phys (and I guess solid-state) knowledge I would definitely call entropy an ensemble property (I'd call it the ensemble property).

I'd guess that you could be talking about mixed-state density matrices, but even that would involve multiple objects, no?

The fuck it is...?

The land of the free I guess

and saying how they would've fucked them had they been alive

That's not how it works.

When one observes an entangled pair, the entanglement is broken.

Bingo! This is effectively the same thing.

However, I have to be a bit pedantic here, in your example the dice might always have been "destined" to be the same, becauase a simple explanation could be that I glued the dice to the bottom of the can, both facing the number 3 up, and that you and a friend measure the same thing because the dice were always going to show 3. This is what we'd call a 'hidden variable theory' and is almost surely not how quantum probability works.

But yeah, entanglement simply means that knowing the outcome of 1 of the experiments gives you some sort of knowledge about the other experiment (like I said, this could be knowing the exact outcome of the other, or just give you better odds than pure luck for guessing the other experiment). The key concept is that you can't control the outcome of the experiments, you just improve your chances of guessing the other experiment correctly, which is exactly what happens in your dice example.

>So no way for instant info exchange?

Reddit was being reddit, so while I could see your reply in my replies, I couldn't find it to reply to. Reply.

I've added a bit at the bottom of my post to explain why. This isn't just aimed at you, I don't know your understanding of quantum mechanics, but I notice that entanglement is a pretty misunderstood topic. And to be honest, actual quantum researchers talking calling their incredibly cutting edge cool research "quantum teleportation" isn't exactly helping this.

Not accepting or even understanding information at a macro level is perfectly understandable. I'm a physicist and I can't marry my knowledge of quantum with the macro world, I don't understand "information" as a quantum concept in macro scale either. (to be honest, I don't think I fully accept "energy" on the various scales)

I think the most simple way to accept "the speed of information" is to just imagine someone transmitting "Hello world", with laser beams through the vacuum of outer space. Since we know that the speed of light is finite, and furthermore light is the fastest thing in the world, no message can get to us faster than a message sent with light. There are lots of caveats to this of course (there always are), but this conceptually at least made sense to me when I first started to learn about this. Once you start to trust this concept, just flip it on its head: the speed of information is 3.00e8 m/s, so there is no way light is faster than information.

(this is a way to get to grips with the concept, this is in no way a proof nor meant as such)

I don't know a lot about cosmology, but I do know about quantum and relativity.

This is a very interesting question! The best way I 'mangle' entangled particles into relativity is to avoid it all together. This is based on the fact that, in order to know about the simultaneity of entangled particles, you'd need a classical channel to transfer information.

Take this experiment: you and I have an entangled particle pair (that's either in AA or BB) and we're lightyears apart. I measure my particle and measure it to be in state A. This means I know yours is in state A too. However, I don't know whether mine is in state A because you collapsed it to be in A, or whether I was the first and have therefore collapsed yours to A. There is no "now your particle is in A" because it could've been there for years (depending on how long ago we separated the particles). The only thing that my experiment proves is that now I know that your particle is in state A. In this way, it's safe to say there is no real simultaneity occurring. This is one of the more prevalent explanations at the moment and one that I personally believe is the most robust since it doesn't require us to completely rip up either relativity or quantum (which are both among the most verified theories we have)

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In other words: to me relativity describes the speed of information. Entangled particles don't break this speed as no information is changing hands. This means there is no shared now between the particles.

(The math also shows this, the order of observations is symmetric (they commute), so they have no impact with regards to causality. No causality = no "now")

Edit: To clear something up, for those who don't live and breathe this stuff: entangled particled are two or more particles that share a common set of states. A "quantum object" (which is not a scientific term, but I'll use it anyway) can occupy a quantized (meaning discrete) set of states. When the object is said to be in a superposition, this object is in an undefined state, where it has an x% chance to be in state A, a y% chance to be in state B etc. When we measure the state of this object, it "chooses" one of these states at random and will be that state.

An entangled state means that two seperate objects share a combined superposition. This means that there are less possible states than just all possible permutations. Eg: two objects who can each be in state A or B and are not entangled if they're in the following (equally likely) superposition: AA, AB, BA and BB. Knowing that the first one is A leaves us with the following possible equally likely states: AA and AB. We know precisely nothing about the second object from knowing the first.

Now an entangled object removes some of these possible states. For example the particles are in a superposition of AA, AB or BB. Now knowing that the first one is B tells us that the second one has to be B too. Knowing the first one is A leaves us with no knowledge on the second one. (they're still entangled though, even if the AA and AB states are really useless)

This is "all" entanglement is. It's not something whereby moving the first from state A to B automatically moves the second one from A to B too.

Since you can't control the outcome of a random measurement, there is no way to encode any information in the entanglement itself that is transported on observation. It's pure probabilistics. I mean, you could make the states in a "superposition" of AA and BA so you know the second person always gets a state A after measuring, but you need to send them the particle which goes with locality, so that's just sending an email with extra steps.

The reason that so called "quantum communication" is so interesting though, is that no one can listen in on your conversation. Take the following scheme:

We agree on the following protocol: We have an entangled pair that's in a superposition of AA and BB. I measure mine, then send you a phone call with my measurement. Then you measure your particle (and therefore verify my phone call, beceause our measurements have to be the same).

If I lie, I mean to transmit a 0, if I speak the truth I mean to transmit a 1

No one knows what we are talking about, because they don't know what our entangled pairs are doing. For them, when I tell you "A", it's either a 0 or a 1, with 50% chance each. However notice I do need to say something to you, because I can't affect the outcome of the observation.

I think this explanation clears up a lot about what entanglement actually is. Some people imagine it's like two switches where if you flip one, you instantaneously flip the other one. It's not.

Tssss, that's what you get for buying a belt-driven vacuum cleaner. I only buy direct drive quartz locked...

More specifically, the smell of fresh rain isn't water, but rather some chemical that's released from the soil.

Is for me?

👉🐶👈

Whoa, I'm in Luzern for the weekend too

>A lot of the book banning fear mongering has been a marketing ploy.

^([citation needed])