Thread: Quantum teleportation across 10 miles

I read that as meaning that the teleportation is instantaneous (ie, not at the speed of light) like gravity is instantaneous (if the sun disappeared, we would be immediately released from orbit, but not see the disappearance for eight minutes).

Anyone know if I got that right?

Originally Posted by MK27

Anyone know if I got that right?

Hmm... this is not your usual self today MK. Seriously, everything alright?

Nothing can travel faster than the speed of light. That includes information.

Originally Posted by Mario F.

Hmm... this is not your usual self today MK. Seriously, everything alright?

Nothing can travel faster than the speed of light. That includes information.

No, but the "entangled particles" bit implies a pre-existing relationship, as with a gravitational "field". As I said -- the effect of gravity is not bound by the speed of light.* Otherwise this would be silly, they are just transmitting.

* does that count as information?

Hope he chokes on that damn thing

If we start excluding things from special relativity on a whim, we might as well exclude special relativity.

Entanglement does not get excluded. It simply is an extension to quantum state. Check the wikipedia article. In this case, essentially you can't describe one photon without observing both. But these are photons we are talking about. So... you know the drill by now. i.e. Speed of Light.

Originally Posted by Mario F.

If we start excluding things from special relativity on a whim, we might as well exclude special relativity.

I understand your little mantra, but you are conceptualizing incorrectly. Again, gravity. The reason the effect of gravity is "instantaneous" is that it is already here. But again, if a sufficient mass were to disappear (which is not possible according to the laws of physics, so your information is still bound), it would not be here. Instantly.

In this case, essentially you can't describe one photon without observing both. But these are photons we are talking about. So... you know the drill by now. i.e. Speed of Light.

Hmm, but the change takes place at the same time -- it does not travel from one photon to the other.

Originally Posted by Brafil

If gravitation is in fact transmitted by special particles (gravitons), this is wrong.

Okay, I had not heard of this one. So gravity remains a mystery and this is an untestable hypothesis (the instantaneousness), what about the entangled particles? Is information transmitted via some connection, or not? I think that possibility is the only thing I find intriguing here...

Originally Posted by MK27

I understand your little mantra, but you are conceptualizing incorrectly. Again, gravity. The reason the effect of gravity is "instantaneous" is that it is already here.

We know very little about gravity. It's unfair for you to quote what is essentially still very early work.

Hmm, but the change takes place at the same time -- it does not travel from one photon to the other.

At which speed do you expect your photon to travel? I suggest you read the source article: Quantum teleportation achieved over ten miles of free space. These photons are traveling.

Originally Posted by Mario F.

At which speed do you expect your photon to travel? I suggest you read the source article: Quantum teleportation achieved over ten miles of free space. These photons are traveling.

Yes, but the "teleportation" is not synonymous with the travelling:

In this particular experiment, researchers maximally entangled two photons using both spatial and polarization modes and sent the one with higher energy through a ten-mile-long free space channel. They found that the distant photon was still able to respond to changes in state of the photon they held onto even at this unprecedented distance.

This still implies to me that the "response" of the second particle is not delayed, since they refer to no means of transmission ("communicating information without needing a traditional signal") etc. Kind of irritating the writer wouldn't consider that worth clarifying.

Since they were discussing doing this from the earth to the moon, if that were the case it would be observable. You could make a request from the moon via normal means, at a 1 second delay, and if the response then triggered on Earth involved a reply using entangled particles, you would not have to wait another second for that reply. You would receive it at the same time as your request was received on Earth (or with whatever microsecond delay was required to trigger on reception of the request).

Of course, if this were the case, probably a bigger deal would be being made because you're right Mario, normally information is presented as bound by the speed of light. There's some details missing here, or I guess we'll be hearing that it can in the future.

Originally Posted by MK27

I understand your little mantra, but you are conceptualizing incorrectly. Again, gravity. The reason the effect of gravity is "instantaneous" is that it is already here. But again, if a sufficient mass were to disappear (which is not possible according to the laws of physics, so your information is still bound), it would not be here. Instantly.



Hmm, but the change takes place at the same time -- it does not travel from one photon to the other.


Okay, I had not heard of this one. So gravity remains a mystery and this is an untestable hypothesis (the instantaneousness), what about the entangled particles? Is information transmitted via some connection, or not? I think that possibility is the only thing I find intriguing here...

Well, I'm no physicist (although I have spent quite a bit of time hanging around the sweaty lot of them (no offense, but almost universally true)), but the general idea is this:

Mass is a condensed form of energy (eg: "light", or electromagnetic radiation), and the quantitive relationship between the two can be precisely described in terms of the speed of light (E=MC^2, Einstein's mass-energy equivalence). Mass (and hence condensed "light") generates a gravitational field (an apparent acceleration), and acceleration generates mass (Einstein's gravity-acceleration equivalence). Their exact values are directly dependant on their Lorentz factor (1/sqrt(1-V^2/C^2)), also described in terms of the speed of light. Logically, then, light, mass, and gravity are essentially equivalent, and so it stands to reason that they must *all* be governed by the speed of light. Okay, so that doesn't actually prove that the distortion of space-time (that is gravity) propagates at the speed of light, per se, but it does describe (more or less) the underlying correlation used by the real mathematicians to deduce that it's value is, in fact, precisely C.

Originally Posted by Sebastiani

Mass is a condensed form of energy (eg: "light", or electromagnetic radiation), and the quantitive relationship between the two can be precisely described in terms of the speed of light (E=MC^2, Einstein's mass-energy equivalence).

Really? That was my impression once upon a time too, altho I have never seen anyone else express it this way, and a while back realized I don't have time to be seriously interested in post newtonian physics. "Mass energy equivalence" does not necessary mean that mass is energy from a conventional perspective -- PSI is not air. Unless you look at it right, I guess.

Okay, so that doesn't actually prove that the distortion of space-time (that is gravity) propagates at the speed of light, per se, but it does describe (more or less) the underlying correlation used by the real mathematicians to deduce that it's value is, in fact, precisely C.

I had another philosophy descended from the "mass is energy" one whereby light didn't have any speed at all and there was no such thing as empty space, there was just light as a medium permitting spacial and temporal (hence the "speed") relations. E=MC^2 would represent a logical barrier in the same way that it already does, or that three dimensions represented a logical barrier. And atomic particles are nodes, of course.

Then I realized I would have to study physics in order to take or present myself seriously and that it wasn't worth it because I wasn't trying to change the rules, just spin them differently. I am kind of cringing from this philosophy now but still see some kind of merit there...I don't think understanding atomic particles as nodes is too far off accepted norms, if you can say "mass is energy" in good company.

Originally Posted by MK27

Really? That was my impression once upon a time too, altho I have never seen anyone else express it this way, and a while back realized I don't have time to be seriously interested in post newtonian physics. "Mass energy equivalence" does not necessary mean that mass is energy from a conventional perspective -- PSI is not air.

Of course they're equivalent - how do you think that stars work? They convert mass into energy!

Originally Posted by MK27

I had another philosophy descended from the "mass is energy" one whereby light didn't have any speed at all and there was no such thing as empty space, there was just light as a medium permitting spacial and temporal (hence the "speed") relations. E=MC^2 would represent a logical barrier in the same way that it already does, or that three dimensions represented a logical barrier. And atomic particles are nodes, of course.

Interesting! I have actually thought the very same thing (but haven't been able to formulate it so concisely). If my math skills weren't so mediocre, I'd probably pursue a theoretical solution to the problem. Unfortunately, being something of an idiot savant, I'm going to have to settle with "having a hunch".