Support NeoGAF

[LordOfChaos]

This is incorrect, the photons were absolutely launched at the station from the ground.

EDIT: Also, manipulating either breaks the entanglement.

Quantum "teleportation" was initially developed in Bell Laboratories and was going to be named something along the lines of quantum state transfer. The PR people decided that it would be better to name it teleportation and thus like the higgs boson "god particle" people suddenly care about it due to its sensational and misleading name. What actually happens with quantum "teleportation" is the quantum state in one particle is transferred to another particle. (eg, the polarization of one photon is vertical on the ground, now it transfers that polarization to a photon in space.) A short version is make a pair of entangled photons send one to space, have a separate photon on earth use the entangled photon on earth to transfer its quantum state to the one in space. Transferring quantum state . Also, object is a pretty misleading term as it makes it seem like the matter is being transferred when as said, its only quantum state information.

tl;dr, Quantum *information* was launched from the ground and instantly received. It's not like a photon walked into a teleporter and then was in space faster than the speed of light.

The article part that says "launched from the ground" that you quoted is unclear or lacks understanding.

 

[Machspeed007]

It's faster than light, but it cannot be used to transfer information.


The particles are only entangled until you measure one of them. At which point, the other particle switches, and the entanglement is broken.

Since you can't know the state of the particle before measuring it, you can't fix the particles to actually transmit any information because they're essentially random while they're entangled.

Furthermore, either side would break the entanglement by actually measuring their particle, so there's no way to actually set up a system in which you could transfer meaningful data anyway.


So, if Side A was on Earth, and Side B was on Alpha Centauri.....Side A could measure all of their particles and know the exact state of Side B. But there would be no way to communicate these findings, since the only way for Side B to know that Side A made a measurement in the first place...would be to measure their particles.

Even if they set up some kind of system, like:

Particle 1 = YES / NO (random)
Particle 2 = If first measurement is correct, break entanglement
Particle 3 = if first measurement is incorrect, break entanglement

This is useless because the only way to know whether or not the entanglement was broken is to either make a measurement, or have someone tell you by some other means...which requires information that is limited by the speed of light.

What if the 2 communication devices with entangled particles are initially in the same spot on Earth and one is taken in a ship to Alpha Centauri. Can you "exhaust" them periodically to communicate instantly?
One pair for transmitting and one pair for receiving, but you know the initial entanglement state for all particle pairs?..

 

[nkarafo]

Soon...

https://www.youtube.com/watch?v=Ro_QpDJX-Sk

First thing that came to mind.

 

[All Possible Ways]

What if the 2 communication devices with entangled particles are initially in the same spot on Earth and one is taken in a ship to Alpha Centauri. Can you "exhaust" them periodically to communicate instantly?
One pair for transmitting and one pair for receiving, but you know the initial entanglement state for all particle pairs?..

Quite generally, you cannot communicate faster than light. The point is that the guy on Alpha Centauri has no clue if you did a measurement or not. On his end, all he can do is measure his own particles and that tells him nothing about if you already measured yours and what results you got. You have to actually tell him, so you can compare notes (you could call him to tell), and that is clearly slower than light.

 

[Moose Biscuits]

Quite generally, you cannot communicate faster than light. The point is that the guy on Alpha Centauri has no clue if you did a measurement or not. On his end, all he can do is measure his own particles and that tells him nothing about if you already measured yours and what results you got. You have to actually tell him, so you can compare notes (you could call him to tell), and that is clearly slower than light.

So basically, this is a non-story to everyone except a small number of physicists.

 

[All Possible Ways]

So basically, this is a non-story to everyone except a small number of physicists.

Excitement depends on the person obviously. You may be disappointed that this is not a miracle sci-fi communicator, but there are plenty of people who are quite excited by the rapid advancements in the field.

To be able to maintain coherence of the entanglement over such long distances is no easy feat, and may pave the way to future technological applications.

 

[Sulik2]

Entanglement means that the two photons are have there spin in lock such that if the photon on earth has it's spin swapped then the one in space changes direction instantly.

Have they confirmed that the transmission of information exceeds what is possible by the speed of light?

The way I have understood this is information is lost in transmission. Reading the particle to tell its spin causes the spin to change so you can't actually transmit info. Which to me just sounds like you need to develop a means to transmit binary by detecting spin changes, not actually caring which spin state its in and you could have FTL communications.

 

[All Possible Ways]

The way I have understood this is information is lost in transmission. Reading the particle to tell its spin causes the spin to change so you can't actually transmit info. Which to me just sounds like you need to develop a means to transmit binary by detecting spin changes, not actually caring which spin state its in and you could have FTL communications.

No information is lost at measurement, rather, no information is transmitted by making a measurement. The measurement is a local process. all you learn is the spin of your particle. Nothing is actually sent to the entangled partner faster than light, so there is nothing you can do to exploit this.

 

[Alexlf]

Quantum "teleportation" was initially developed in Bell Laboratories and was going to be named something along the lines of quantum state transfer. The PR people decided that it would be better to name it teleportation and thus like the higgs boson "god particle" people suddenly care about it due to its sensational and misleading name. What actually happens with quantum "teleportation" is the quantum state in one particle is transferred to another particle. (eg, the polarization of one photon is vertical on the ground, now it transfers that polarization to a photon in space.) A short version is make a pair of entangled photons send one to space, have a separate photon on earth use the entangled photon on earth to transfer its quantum state to the one in space. Transferring quantum state . Also, object is a pretty misleading term as it makes it seem like the matter is being transferred when as said, its only quantum state information.

tl;dr, Quantum *information* was launched from the ground and instantly received. It's not like a photon walked into a teleporter and then was in space faster than the speed of light.

The article part that says "launched from the ground" that you quoted is unclear or lacks understanding.

I... agree? I'm not sure which of your posts I'm misunderstanding, but I was disagreeing with the "the photon didn't move from the ground to space" from your other post. The photon's were absolutely launched from the ground, as you're agreeing with in this post I think? As far as I'm understanding the story they would entangle a pair of particles, launch one of the photons into space and then measure it's spin at the station until they got some that remained entangled, right?

And any gross manipulation with the particle DOES break enlargement; You can measure it and get the same result at either end, but actually affecting the spin of the particle in an intentional way breaks the entanglement. That's all I was commenting on with the quote about manipulating it