Quantum entanglement

[Engyo]

Originally Posted by little_monkey

You are confusing the particle A with the photon it must send to particle B to get its message across.

In case you haven't understood the experiment. At center, two particles are sent in opposite directions, one towards Alice (A), the other towards Bob(B). In order for the first particle (traveling to A) to communicate with the second particle (traveling to B) it must send a photon. That photon can only travel at lightspeed. Therefore the measurement by Bob(b) can take place way before the photon arrive.

BTW, I did not invent this experiment, it was first designed by Schrodinger in 1935.

I don't believe that a photon is sent between the particles.........I think it is that they are linked in some way we don't yet clearly understand, and that to change one is to change the other with much much less than a light-speed delay - which is what quantum entanglement means. If it were necessary to send messages (photons) between the particles then they couldn't be said to be "entangled", could they?

[little_monkey]

Originally Posted by Engyo

I don't believe that a photon is sent between the particles.........I think it is that they are linked in some way we don't yet clearly understand, and that to change one is to change the other with much much less than a light-speed delay - which is what quantum entanglement means. If it were necessary to send messages (photons) between the particles then they couldn't be said to be "entangled", could they?

The experiment can go on with or without a photon being sent.The entanglement has nothing to do with the photon. The question of the photon was raised in response to what relativity allows in this experiment, which is that whatever information can take place, that info is restricted by relativity.

The word "entanglement " was used by Schrodinger to signify that somehow there was a connection between the particles as they travel through space, tho' that connection is a mystery. Einstein wrote a paper, often referred as the EPR paradox, in which he was trying to refute the claims made by quantum mechanics.

Read more at: EPR paradox - Wikipedia, the free encyclopedia

[Jaiket]

On the topic:

Speed of 'instantly' calculated

You have to travel very quickly to be somewhere "in an instant", say scientists - at least 10,000 times the speed of light, to be precise.

Physicists have worked out the speed of "instantly" with an experiment investigating the weird phenomenon of quantum entanglement that connects paired particles.


Channel 4 - News - Speed of 'instantly' calculated

[Troublemane]

Originally Posted by little_monkey

You are confusing the particle A with the photon it must send to particle B to get its message across.

In case you haven't understood the experiment. At center, two particles are sent in opposite directions, one towards Alice (A), the other towards Bob(B). In order for the first particle (traveling to A) to communicate with the second particle (traveling to B) it must send a photon. That photon can only travel at lightspeed. Therefore the measurement by Bob(b) can take place way before the photon arrive.

BTW, I did not invent this experiment, it was first designed by Schrodinger in 1935.

Nope, i am not confusing anything. You havent paid attention to my explaination. The two particles sent in opposite directions are travelling at either light speed or near light speed, and relativity says that time and space (relative to a particle moving near or at lightspeed) shrinks to zero. So what I am saying is that the two particles flying away from each other at light speed do not experience any time change until they strike the detectors at opposite sides of the galaxy or ..arbitrarily far away.

since they experience no time change they experience no spatial changes either, so from their reference they are still together as one. THATS why we can have one go thru the detector, measured as "up", and know that simultaneously the other has now changed to "down"---because they were both really just the same particle until the moment we measured one.

there really is no mystery about it, unless you insist on believeing in "local" reality as the only reality (i.e.,anything not going light speed).

[little_monkey]

Originally Posted by Troublemane

Nope, i am not confusing anything. You havent paid attention to my explaination. The two particles sent in opposite directions are travelling at either light speed or near light speed...

The two particles moving away DO NOT need to travel at lightspeed for QE to take place. They can be moving at 3 x 10ˆ4 m/s, an insignificant fraction of the speed of light. Hence, no time dilation and no space contraction can be be invoked to explain QE.

[Troublemane]

then this is not a quantum entanglement experiement

[little_monkey]

Originally Posted by Troublemane

then this is not a quantum entanglement experiement

Read my post #12.

[Troublemane]

the particles have to be subatomic scale in order for quantum effects to be observed, and these particles have two speeds: near light speed, and complete stop. sorry dude, you cant have quantum entanglement between two particles going slower than lightspeed or near light speed, its impossible.

[little_monkey]

Originally Posted by Troublemane

the particles have to be subatomic scale in order for quantum effects to be observed, and these particles have two speeds: near light speed, and complete stop. sorry dude, you cant have quantum entanglement between two particles going slower than lightspeed or near light speed, its impossible.

Most particles at sub-atomic level move with a speed ≅ 10ˆ5 m/s. Are you saying that electrons and quarks can only exist at the speed of light???