# Properties of entanglement between particles

#### benit13

What determines the formation of entanglement between two particles? Is it just a distance between two particles which have not yet conferred a state/spin?
Pair production is the main one. I don't know anything about the other methods, but apparently there are other methods.

I read online that different types of particles like photon and electron could become entangled. Is this true?
Can one particle be entangled to only one or two or more other particles?
Yep, but I don't know anything about it!

Could entangled particles be unentangled?
What if one photon that undertook a state becomes absorbed and its energy converted. What will happen to its previously entangled counterpart, will it lose state and return to a wavefunction?
Entangled particles behave like a single system, so absorption of one photon is actually a partial absorption of the whole. I don't know what that would look like.

#### GatheringKnowledge

Entangled particles behave like a single system, so absorption of one photon is actually a partial absorption of the whole. I don't know what that would look like.
Now this is some awesome property of entanglement, that doesn't seem to be as widely discussed, as some other effects. Just think about the implications and future possibilities: wireless & instant transfer of energy with unlimited distance...(?) Hmm, probably I know now, why this subject seems to be kept at the bottom of the drawer...

#### topsquark

Forum Staff
Now this is some awesome property of entanglement, that doesn't seem to be as widely discussed, as some other effects. Just think about the implications and future possibilities: wireless & instant transfer of energy with unlimited distance...(?) Hmm, probably I know now, why this subject seems to be kept at the bottom of the drawer...
It would be nice if we could use entangled particles in this way but QM, as always, is probablilistic so when you make a measurement it's still random. It's only when we get the two pairs of data together (ie both people who do the measurement meet each other) that we see the pattern.

-Dan

#### studiot

I have always understood that entanglement works like this.

If we add one red ball to a bag of black ones, shake well and draw a ball at random, then transport the bag of remaining balls to the other end of the universe, we will be able to tell the colour of the next ball to be drawn (by zaphod beeblebrox) if the ball we have drawn and kept at home is red.

#### GatheringKnowledge

It would be nice if we could use entangled particles in this way but QM, as always, is probablilistic so when you make a measurement it's still random. It's only when we get the two pairs of data together (ie both people who do the measurement meet each other) that we see the pattern.

-Dan
To be honest, I was speaking about the idea, that energy absorbed by one of entangled particles, will be shared among the entangled pair. In the difference to other types of measurement, learning about the current energy state of a particle, won't necessary cause it's wave function to collapse - as we just need to look at the frequency of vibrations... But on the other hand, any kind of energy transfer = way to transfer information, so it's good that you mentioned it...

Yes, I know the way, in which science tries to deal with the problem of instant information transfer, by finding a way around it. Sadly, it is not that hard, to find a possible solution. All what is needed, is to assign one of entangled particles as a receiver and second one, as a source/emiiter. The source-particle can be then placed onboard a spaceship with the instruction, to collapse it's wave function at some specific coordinates and maintain such state for a period of time. At the same time, in the frame of receiving particle, we start to make repeating measurements of state at some choosen frequency. So - When the wave function of source-particle will collapse at proper coordinates and remain collapsed for some time, receiving particle will continue to gain reversed state during all the measurements, which will be made after the collapse in source's frame - so, receiving frame will get the information, that spaceship reached a specific location.

#### topsquark

Forum Staff
Let's say we have someone on Earth and someone on, say, the Moon. Imagine there is a beam of particles going from the Earth to the Moon. Let's put a dector on Earth and another on the Moon and let's measure the spin in the +z direction. The process to create the beam is going to random. (We can work polarized particle beams if you like, but it would be boring because you'd keep getting the same result each time you measured.) The particle passes into the setup on Earth and thus the Moon will measure the opposite spin. But again the process creating the beam is random. So we would get a list of spins 1/2, 1/2, -1/2, 1/2, -1/2, -1/2, 1/2, etc. The list generated on Earth would be random and thus the Moon's reading will appear to be random as well.

As to turning the beam on and off at particular locations that's all fine and good but recall that you have to have the beam sent by Earth to the Moon. Yes, there is an entanglement here that can be used, but bear in mind the particle beam has to get to the detector before the spin can be recorded. You can simply use a beam of your favorite massless particle to do the same thing.

-Dan

#### GatheringKnowledge

Let's say we have someone on Earth and someone on, say, the Moon. Imagine there is a beam of particles going from the Earth to the Moon. Let's put a dector on Earth and another on the Moon and let's measure the spin in the +z direction. The process to create the beam is going to random. (We can work polarized particle beams if you like, but it would be boring because you'd keep getting the same result each time you measured.) The particle passes into the setup on Earth and thus the Moon will measure the opposite spin. But again the process creating the beam is random. So we would get a list of spins 1/2, 1/2, -1/2, 1/2, -1/2, -1/2, 1/2, etc. The list generated on Earth would be random and thus the Moon's reading will appear to be random as well.

As to turning the beam on and off at particular locations that's all fine and good but recall that you have to have the beam sent by Earth to the Moon. Yes, there is an entanglement here that can be used, but bear in mind the particle beam has to get to the detector before the spin can be recorded. You can simply use a beam of your favorite massless particle to do the same thing.

-Dan
Ok, your arguments seem to be valid in this case - however, this is mostly because you've used a scenario, that creates an "artificial debility" in the process of information exchange in an entangled system. Since your scenario includes a beam of particles, that has to obey the limit of constant c, we end up with a "crippled" process of information transfer. If you want to make a theoretical test of the idea of entanglement, that allow a FTL data transfer, try using a scenario, which won't involve data transfer at c. Better would be to discuss a situation, where pairs of entangled particles (electrons from a single orbital) don't experience any delay, when the state of distant particle is determined by the measurement, that is made in "our own" frame.

But things will look even worse for the mainstream science, if we will use the process, which benit13 mentioned in his post, as it won't even need to use the process of wave function collapse, to directly change the state of a distant particle due to entanglement - we need only to increase the energy level for one of entangled particles and half of that energy will be transferred in some spooky way to the second particle. While other processes associated with entanglement cause already a lot of chaos and confusion - that one is a real game-changer. I'm trying to stay up to date, when it comes to science and technology, but I admit, that I went through a small mental shock, when I read it here..

#### topsquark

Forum Staff
Better would be to discuss a situation, where pairs of entangled particles (electrons from a single orbital) don't experience any delay, when the state of distant particle is determined by the measurement, that is made in "our own" frame.
The measurement of a property happens FTL, this is true. You measure one particle and the state of the other entangled particle will fall into the corresponding state. But there is no way around having to get the particle to the other site to measure it. That's just the basic fact. Now, once the particle is there then maybe we can extrapolate a bit using SR but it makes no difference in the end.

Sorry, but the entangled information transfer concept just doesn't work. Benet13's idea is a nice idea but it won't work. I'm not saying that as a protector of "mainstream science." QM follows the rules that it does... There are very few processes that don't take part in QM's built in randomness. It's just the nature of the beast.

-Dan

donglebox

#### benit13

Sorry, but the entangled information transfer concept just doesn't work. Benet13's idea is a nice idea but it won't work.
I agree. Just to clarify, I never suggested entanglement can be used for FTL information transfer.

topsquark

#### GatheringKnowledge

But there is no way around having to get the particle to the other site to measure it
But why should we? If one particle is measured to have it's spin "up", second one will have it's spin "down" - we don't have to measure the second paricle, to know, what is it's actual state...