about entanglement and time

[Itoero]

If entanglement goes faster then the speed of light...shouldn't it influence time?

[ajb]

If entanglement goes faster then the speed of light...shouldn't it influence time?

 

The important thing to remember is that one cannot transmit information faster than the speed of light, this is how we today understand the notion of causality. There is no violation of the principles of special relativity and so no obvious need to modify what we mean by time.

 

Maybe you can elaborate on what kind of influence you mean?

[Itoero]

The collapsing of the entanglement goes faster then the speed of light.

That imo points to the fact hat entanglement uses a frame that stands outside time and space.

I don't know how, but it should influence time if the notion of space time is correct.

 

The important thing to remember is that one cannot transmit information faster than the speed of light,

In Quantum teleportation info is transmitted in the same frame as entangled particles do.

If entanglement goes FTL then teleportation should go FTL as well.

[swansont]

The collapsing of the entanglement goes faster then the speed of light.

 

There are phenomena which go faster than the speed of light. It's not inherently a problem unless there is a causal connection between them.

 

Take a lighthouse light, and pretend it's really bright. It revolves at 1 revolution per minute. We could imagine constructing a screen very far away from it and watch the light move across it. At some distance, the speed of the lit part will exceed c (left as an exercise to determine this distance). No violation of relativity has occurred. There is no causal connection between when each photon hit the screen.

[ajb]

The collapsing of the entanglement goes faster then the speed of light.

As swansont points out, by itself this is not a problem. We have no violation of causality as no information can be exchanged in this way.

[Eise]

In Quantum teleportation info is transmitted in the same frame as entangled particles do.

If entanglement goes FTL then teleportation should go FTL as well.

 

No:

 

Quantum teleportation is a process by which quantum information (e.g. the exact state of an atom or photon) can be transmitted (exactly, in principle) from one location to another, with the help of classical communication and previously shared quantum entanglement between the sending and receiving location. Because it depends on classical communication, which can proceed no faster than the speed of light, it cannot be used for faster-than-light transport or communication of classical bits.

 

 

Bold by me.

[Itoero]

There are phenomena which go faster than the speed of light. It's not inherently a problem unless there is a causal connection between them.

 

Take a lighthouse light, and pretend it's really bright. It revolves at 1 revolution per minute. We could imagine constructing a screen very far away from it and watch the light move across it. At some distance, the speed of the lit part will exceed c (left as an exercise to determine this distance). No violation of relativity has occurred. There is no causal connection between when each photon hit the screen.

True, but measuring or teleporting is the cause...

 

Because it depends on classical communication, which can proceed no faster than the speed of light, it cannot be used for faster-than-light transport or communication of classical bits.

What's classical about the communication? You send classical info but that doesn't make the communication to be classical.

[swansont]

True, but measuring or teleporting is the cause...

Flip a coin. You see whether it's heads or tails, and immediately know what the reverse side is. That would be true even if the coin were 1 light-second thick. Or a light-minute. Etc. No causality violation.

[imatfaal]

What's classical about the communication? You send classical info but that doesn't make the communication to be classical.

 

Because the quantum information is completely useless unless read in conjunction with the classical information - so the speed of transmission is the speed of the transmission of the classical information. To teleport a quantum state relies on a previously shared bell pair which is transformed via unitary translation and measured by the sender - the results of the measurements are passed on which allows second party to perform (or not)unitary translations on his half of the bell pair and his half of the bell pair ends up in the same as the senders[vastly simplified]. The quantum state has been teleported (not reproduced as the initial copy is lost in measurement) at the cost of two bits of classical information and the loss of the bell state pair

[TakenItSeriously]

While FTL communication could not be done between two parties, one possible use for this type of information transfer would be for sending encryption keys to two parties who could then securely send messages to each other via conventional means.

 

The keys would be nondeterminately random to everyone else but the two parties who received them. Im not sure how cost effective it would be but it proves that secure two party communication without a trusted third party intermediary is theoretically possible which is a big deal in some circles.

 

I Doub't that's what you had in mind when talking about changing time though.

Edited January 17, 2016 by TakenItSeriously