# B Quantum entanglement comunication

1. Feb 14, 2019 at 5:15 AM

### Paulo Jardim

I have a question about quantum entanglement, I see saying that it would not be possible to communicate faster than light using this technique, but for example, and I understand that it is not the information that travels, however if for example we use the interval of the measurement and read as binary, that is to say the if it was measured so result = 1 if not so = 0, or as Morse code, in short, it would not be possible to read in if it was measured or not and the result translate for information?

2. Feb 14, 2019 at 6:22 AM

### Staff: Mentor

It is impossible for Bob, working alone in his lab, to know whether Alice has done anything with her particle.

Entanglement only reveals itself when Alice and Bob share information about what they did with their particles and what the results were.

3. Feb 14, 2019 at 6:25 AM

### Paulo Jardim

Yes, if they create protocol, like internet only works because they have a protocol!

But why I need the Alice result if I know what was?

4. Feb 14, 2019 at 6:30 AM

### Staff: Mentor

This has no relation to what we are talking about.

If you have no information from Alice, your ensemble of particles will look random. You have to compare the Alice's result to even determine that the particles were entangled in pairs to begin with.

Coming back to the OP:
By looking only at his particle, Bob has no way of knowing whether Alice has measured her particle or not.

5. Feb 14, 2019 at 6:47 AM

### Paulo Jardim

I thought that once the measurement was made by Bob, then the particle could be read, but that is not the case, so I understand there is no way of detecting that there was a measurement.

Thanks Dr.Claude

6. Feb 14, 2019 at 6:56 AM

### Paulo Jardim

would it not be possible to force the particle to be measured in a specific state and thus apply in identical intervals between the two sides and compare the results?

sorry for the stupid questions*

7. Feb 14, 2019 at 7:07 AM

### PeroK

That's exactly what is not possible. The initial measurement of each particle is correlated. But, anything you do to the particle after that is not reflected in the other particle. The first measurement breaks the entanglement.

8. Feb 14, 2019 at 7:48 AM

### Paulo Jardim

This I understood, my experiment was to take several entanglement waves, organize them to identify them, I imagined that when (Bob) did the reading here would be possible (Alice) knew that it was made, since there would be a wave collapse and in this way you could know that there was a measurement.

PS.

Well, thinking about it would only work if we could do the measurements without changing the properties of the particle, which if I'm not mistaken is improbable.

Last edited: Feb 14, 2019 at 7:59 AM
9. Feb 14, 2019 at 8:34 AM

### Staff: Mentor

Collapse is only part of one interpretation of the theory. It is not something physical, so there is nothing the observe.

Entanglement means that the state of each particle can't be expressed independently of the state of the other. A measurement will necessarily break the entanglement, since the state of each particle is then independent of the other.

10. Feb 14, 2019 at 8:36 AM

### Paulo Jardim

It`s crystal now, thanks guys!!!

Regards,
Paulo Jardim