# Time Delay Information Transfer with Entangled Particles

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• jackmiller2003
In summary, the thought experiment can be solved by either using pre-ordered particles or encoding the timing of the measurements.
jackmiller2003
TL;DR Summary
Why can't information be sent via Quantum Entanglement through the time between the measurement of entangled particles?
Hello, my name is Jack and I'm a year 11 student in Australia. After listening to, and reading some information regarding quantum entanglement, I'm still a little unsure about the solution to a thought experiment:

Let's say that I create a situation in which multiple pairs of particles are entangled at a particular place and each partner in the pair is separated into one of two different groups. One group is sent 100 km in one direction and then other group is sent 100 km in the other direction. Couldn't you use the time delay between observation of each particle as a means of FTL communication? Say 1 second between particle measurement means a 0 in binary and 2 seconds means a 1 in binary. Hypothetically, with enough particles, couldn't you send meaningful messages faster than light?

Any help would be much appreciated!

Thanks, Jack.

P.S: The thought experiment could also work by pre-ordering the particles in a row to send information.

Sorry if I've totally missed something obvious!

jackmiller2003 said:
Couldn't you use the time delay between observation of each particle as a means of FTL communication?

No, because observers on each side don't know when the particles on the other side are measured.

jackmiller2003
PeterDonis said:
No, because observers on each side don't know when the particles on the other side are measured.

Oh so the influence of measurement on one side can only be determined by measurement on the other side? Is it correct to say that if observer A has collapsed the wave function, observer B still believes there is a wave function because they haven't measured it?

jackmiller2003 said:
so the influence of measurement on one side can only be determined by measurement on the other side?

Not even that. To see the influence you have to compute the correlations between the measurement results on both sides. You can only do that when you have both sets of results communicated to you by ordinary slower-than-light means. The measurements on either side by themselves will simply look random and give no information about what's going on on the other side.

jackmiller2003
PeterDonis said:
Not even that. To see the influence you have to compute the correlations between the measurement results on both sides. You can only do that when you have both sets of results communicated to you by ordinary slower-than-light means. The measurements on either side by themselves will simply look random and give no information about what's going on on the other side.

Even if the timing of the measurements are encoded? For example, if you have two particles which are entangled based on Z-spin, wouldn't the measurement of one result in the opposite result in the other?

P.S: I'm not trying to be at all combative, just trying to work out my misconceptions :)

jackmiller2003 said:
Even if the timing of the measurements are encoded? For example, if you have two particles which are entangled based on Z-spin, wouldn't the measurement of one result in the opposite result in the other?

P.S: I'm not trying to be at all combative, just trying to work out my misconceptions :)
Look at it this way. You measure Z-spin. You get "up", so you know the other person (if they also measure Z-spin) gets "down". You haven't really communicated anything to them or them to you. You haven't sent a message. Think of it like generating a bunch of 0s (up) and 1s. (down) You get:
010100111100000...
They'll get the same with the 0s and 1s flipped. Both of you just get related random strings, but it's not really a message from you to the other person.

It can be used to have a shared "secret" password, but not communication.

jackmiller2003 and PeroK
jackmiller2003 said:
Even if the timing of the measurements are encoded? For example, if you have two particles which are entangled based on Z-spin, wouldn't the measurement of one result in the opposite result in the other?

P.S: I'm not trying to be at all combative, just trying to work out my misconceptions :)

Keep in mind: All that anyone sees (on either side) is a string of random outcomes. It is pretty hard* to get a message from a random string. So no matter what the relationship between them is, the actual sequence itself is still random. That is axiomatic for entanglement, where the system is in a superposition of states.*I.e. impossible.

jackmiller2003 and vanhees71
jackmiller2003 said:
if you have two particles which are entangled based on Z-spin, wouldn't the measurement of one result in the opposite result in the other?

Yes, but you can't control in advance which one will be spin up and which one will be spin down for each pair of particles; that's random. So there's no way to encode anything in the sequence of up/down results.

jackmiller2003 and vanhees71
jackmiller2003 said:
Even if the timing of the measurements are encoded? For example, if you have two particles which are entangled based on Z-spin, wouldn't the measurement of one result in the opposite result in the other?

P.S: I'm not trying to be at all combative, just trying to work out my misconceptions :)
Suppose you want to send your friend a message at a predetermined time. You and your friend have a pair of entangled things.

Your code is: up = do something; down = do nothing.

You want your friend to do something. So, you go to your entangled particle and measure it. But, you get "up", so you know your friend will get "down". Bad luck! You just sent the wrong message, if we can put it like that.

In measuring your particle you cannot control the outcome. You cannot control your friend's outcome, so you cannot send a message.

All you have is some shared data that nature has provided. Which is still something useful, but it's not a message from you to your friend.

Indeed, but the great thing is you can prove the correlations due to entanglement, but only after both experimenters have done their experiment and stored it in a measurement protocol by exchanging the information contained in their measusrement protocols, and that can not be done with any signal faster than light, i.e., there's no way to communicate with faster-than-light signals even when exploiting quantum entanglement. That's also by construction "encoded" in the mathematical formalism describing relativistic quantum theory, which is relativistic quantum field theory, as applied in the Standard Model of elementary particle physics.

jackmiller2003
Thanks for everyone's replies, very helpful.

Although I had understood the idea that measurement results in a random outcome, I had forgotten that both observers needed to make a measurement of the particle in order to see its result. My original thought experiment assumed that measurement on one side would allow the other side to see the influence without them measuring the particle themselves which is clearly wrong!

Once again, thanks!

vanhees71

## 1. What is time delay information transfer with entangled particles?

Time delay information transfer with entangled particles is a method of transferring information between two distant locations using entangled particles. This means that the particles are connected in a way that their states are correlated, regardless of the distance between them. Through this correlation, information can be sent from one particle to the other, even if they are separated by large distances.

## 2. How does time delay information transfer with entangled particles work?

This process works by first entangling two particles, which means that their states become correlated. One particle is then sent to a distant location while the other remains at the original location. When a change is made to the state of one particle, the state of the other particle will also change instantaneously, regardless of the distance between them. This allows for the transfer of information between the two particles.

## 3. What is the advantage of using entangled particles for time delay information transfer?

The advantage of using entangled particles for time delay information transfer is that it is nearly instantaneous, regardless of the distance between the particles. This means that information can be transmitted faster than the speed of light, which is the maximum speed at which information can travel through traditional methods. Additionally, entangled particles are highly secure, as any attempt to intercept or measure the particles will cause their entanglement to collapse, alerting the sender and ensuring the privacy of the information being transmitted.

## 4. What are the potential applications of time delay information transfer with entangled particles?

There are many potential applications for this technology, including long-distance communication, quantum computing, and quantum cryptography. It could also be used in space exploration, where traditional communication methods are limited by the vast distances involved. Additionally, it has the potential to greatly improve the speed and security of information transfer in various industries, such as finance and healthcare.

## 5. Are there any challenges or limitations to using time delay information transfer with entangled particles?

While this technology has many potential applications, there are still some challenges and limitations that need to be addressed. One major challenge is maintaining the entanglement of particles over long distances, as any interference or noise can disrupt the correlation between the particles. Additionally, the technology is still in its early stages and requires further research and development before it can be widely implemented in practical applications.

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