# Sending information via quantum entanglement?

1. May 31, 2010

### Superstring

Suppose you have a set of two particles and each of those particles is entangled with another particle in a corresponding set. You could cause wave function collapse of one of the particles to signify a 0 bit, or you could cause collapse of both particles to signify a 1 bit. The configuration on the receiving end could then use a double-slit-esque device to determine which of them have collapsed. Supposing you had enough entangled material, wouldn't it be theoretically possible to send information this way?

Last edited: May 31, 2010
2. May 31, 2010

### magpies

It doesn't work currently because of the fact that you can't look at it all the time so the 2nd party has to guess when to look at it and by doing so they effect it anyhow.

3. May 31, 2010

### Superstring

They could be using synchronized clocks and a previously agreed upon time.

4. Jun 1, 2010

### haael

The receiving end has no means to determine whether the sending end has done any collapse. The double-slit experiment will give the same result. It doesn't matter if the other party looked at their particles.

In fact, hardcore QM says that the receiving party will go into quantum superposition.

Also, double-slit experiment is a statistical effect. You have to have a large number of particles to have an interference pattern. Single particle would just hit the screen at some random point and you wouldn't know whether it meant to draw the pattern or a simple circle.

The point is: quantum entanglement can only transfer correlation, not the information itself. You can create some random number in two separate places in universe. This could be used for cryptographic keys or for cheating in some games, but you don't have any control of the exact value of the number. So sending information faster than light is impossible.

5. Jun 1, 2010

### JDługosz

Suppose we each have an electron, entangled so the total spin is zero.

What can I do to "collapse one" or "collapse both"?

The only thing I can do is make a measurement of mine, which collapses both. That's what entanglement means.

Worse, you can't tell whether or not I've made such a measurement, because the time doesn't matter. You can look at yours first! More generally, which is first is dependent on the reference frame and being spacelike separated there is no time ordering of our two measurement events.

Given the spin entanglement, which is the normal (simplest) example of an entangled system, the measurement to perform is to measure the spin on some chosen axis.

No. It is shown to be mathematically impossible to transmit information this way.

6. Jun 1, 2010

### Geigerclick

Bottom line: No Classical means of confirmation, and the answer to the OP is a simple, "No."

7. Jun 1, 2010

### rathat

I wouldn't think so, but it would be INCREDIBLE if you could.

8. Jun 2, 2010

### Geigerclick

It would be incredible if I could fly by will alone; alas.

9. Jun 3, 2010

### Demystifier

Very recently, I have found that entanglement can be used for a sort of superluminal (faster than light) communication, provided that free will is merely an illusion:
http://xxx.lanl.gov/abs/1006.0338

10. Jun 3, 2010

### unusualname

lol, if FW was an illusion I doubt that paper could have been composed. I like the bit where they say (of preparing the external influence on the brain) "Of course, there may be many technical difficulties to achieve this in practice, but it is conceivable that all these difficulties will be resolvable by an advanced technology"

Don't worry humanity, I'm pretty sure FW exists, and I don't think it's long before these QM "mysteries" will be looked back on with some hilarity.

There is no known way classically to cause a quantum particle to select a definite state, hence there is no known way to transmit classical information.

However, for all you frustrated searchers of truth I'll propose a very reasonable resolution to all this:

If you actually are the quantum system then you can deterministically select quantum states, which gives you free will :) (thank god for that ;) )

Now all we require is that consciousness is an entangled quantum system cleverly built by evolution.

And then we need to assume that quantum processes (and hence our thoughts) exist in some non einsteinian space. But that's reasonable, since I don't see how I could be consciously aware of the same space in which my conscious awareness exists.

So you can't send classical information via quantum entanglement since you can't prepare a quantum state deterministically using classical influences.

But you can send quantum information, and hence if two brains can one day be entangled and separated by a large distance they will be able to communicate FTL, although they won't be able to use this information to cause any classical effects FTL (so it may be a frustrating experience ;) )

This solves free-will, consciousness, QM theory of GR (you don't need one, QM operates on a different space) and all the interpretation problems of QM.

Right, that should make the models of einsteinian space easier, now that we've separated out QM mechanisms into their own space. The exploration of this new space will preoccupy the next stage of Science, and everyone can have a laugh over how they missed the obvious for ~100 years

(For the romantics among you, you might consider the possibility of love being due to partial entanglement of separate consciousnesses, but I think it's unlikely)

11. Jun 4, 2010

### Zarqon

It's an interesting read and I agree that free will being an illusion is likely, see my further comment below.

(I saw it already yesterday on the archives, and as for comments may I start by the small remark that welcome is with one 'l' :tongue: )

I don't see any arguement behind this reasoning, so what makes you so certain?

For myself, I'm having a hard time even defining what Free Will is. It seems to me that the universe is either truely random or it is deterministic (though we don't yet know which).

In the former case, if it's truely random, how exactly can we call something free will, with an emphasis on will. It could certainly be said to be free, but what exactly is 'will' if everything boils down to random events?

In the latter case, if the universe is deterministic, then it's clear that there is no free will, as everything is predetermined in some sense.

Thus, in either case, there is no free will.

It seems likely that free will is indeed an illusion, caused by a, if not quantum, then at the very least chaotic complexity of the brain.

12. Jun 4, 2010

### Demystifier

Zargon, I completely agree with you.

Although, there is a logical possibility that a part of nature is neither probabilistic nor deterministic. In that case, this part is not described by the known laws of physics. In terminology of my paper above, in that case the laws of physics are not universal. That is the only way to save free will (for those who want to save it).

(And thank you for your remark which is very welcome!)

13. Jun 4, 2010

### zonde

Free will is our ability to promote initially random insignificant event to the level of high significance.
So it requires for there to be randomness and certainty at different scale levels. Because this process is initiated by random seed but process itself is deterministic.

14. Jun 4, 2010

### unusualname

You think I worked out my proposal on the back of an envelope? Here's the abstract from my upcoming paper to arXiv:

Then Gravity is just a theory of classical (einstein) space.

Our consciousness is part of quantum space and hence we can deterministically manipulate quantum space. Until consciousness evolved, quantum events were occuring randomly and the universe was just statistical physics. That's kind of obvious really, since the alternative is no free-will which is clearly silly, you have to explain how these ridiculous conversations are generated otherwise .

Imagine you had to create a deterministic universe allowing free-will, you'd create a physical deterministic space and a coexisting space where random events occur, and then beings with free-will would be emergent entities in the random space, emergent entities that have deterministic control over the random events since in fact they then "are" the random events. I really don't see how it can be any other way without invoking religious or other mystical nonsense.

I probably should have made clear that communication in entanglement and hence in "quantum space" need not be instantaneous, in fact may be limited but by a higher velocity than c, say c^k for some small integer k. This gives an experimental test of this proposal, since it implies that entanglement effects will not be instantaneous but have some (small) delay.

Although we'd need to understand the topological relation of this "quantum space" with classical space before speculating on communication bounds, ie. how does quantum space "mesh" with classical space, continuously (eg extra euclidean dimensions), discretely (eg lattice structure coexisting with classical space) or some intricate (and compactified) calabi-yau type construction?

Of course, it's not just the observation that consciousness is not part of the physical world that leads to this model (but it is a big inspiration), also we have the small problem of missing most of the universe described by classical space. :)

15. Jun 4, 2010

### jambaugh

I am sorry but I am predestined to believe in free will.

16. Jun 4, 2010

### Zarqon

Just pointing out, "is clearly silly" will hardly convince anyone who did not agree with you from the start, hence my remark on wanting an arguement.

To zonde/unusualname: Let me try to give a definition of conciousness/"illusion of free will" that does not require any true randomness.

I imagine the conciousness/free will in our brain (or illusions thereof) as just a complex set of reflexes and information filters. If you go back a billion years or so and see how the first organisms developed simple reflexes, that made them for example move towards lighter areas, or move when something poked them, or change shape or similar things. Very basic reflexes, but as organisms became bigger and more complex, these reflexes also became more complex, and with better and more senses involved, information filters was added to the sensory input. It seems likely that the brain is simply a large collection of such information filters and reflexes that now involve so complex interactions, that we simply cannot see the individual pathways (think chaotic), and so we experience the outcome of signals having gone through this machinery as "free will".

In this sense, I would define conciousness simply as being each persons collection of filters and reflexes, and this description works regardless of whether the universe is deterministic or random, because the seeds for this machine are external inputs (through any senses).

This can also explain why we have this strange conversation, because it's evolutionary benefitial to be curious and gather information, so that's what the outcome of the filtering machinery will be.

However, it is still difficult to say that a collection of reflexes and filters really possess true "free will", because although it's very complex and impossible to fully predict, in the end, it may just be an automated response to your environment.

17. Jun 4, 2010

### Geigerclick

I assume this is just your own pet theory, and not backed by anything not on the rear of an envelope? If so, this is not the place for it.

18. Jun 4, 2010

### unusualname

The existence and destruction of the universe doesn't make sense without randomness (and free-will)

Theoretically we can choose to destroy the universe, eg by constructing some self-replicating machine to create black-holes all over the universe (although admittedly that would take along time), in fact there are probably a countable infinity of ways we could choose to destroy the universe.

This is a reductio ad absurdum argument against super-determinism, since the universe would have only one way of being destroyed in a purely deterministic universe.

You have to have randomness, and since classical space is deterministic we must have another space which is not. (And in fact we need this space for consciousness, since we can not be conscious of the same space in which our consciousness exists)

From randomness we can get emergent properties, such as our free-will, which is consciousness determistically selecting quantum states in an entangled quantum system.

19. Jun 4, 2010

### unusualname

Just to clarify that I'm now only responding to the point raised by the OP and Demystifier's link to a paper which claims classical information can be sent via entanglement if we give up free-will.

And to further clarify the argument I made, that since we can conceive of many possibilties for bringing the universe to an end (uniform entropy) by logical reasoning, if those possibilities are not in fact possible then we must admit that logical reasoning is wrong.

So no free-will => logical reason is wrong