What Are the Key Experiments and Applications of Momentum Entanglement?

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Discussion Overview

The discussion revolves around momentum entanglement, specifically exploring key experiments and applications, as well as the implications of accelerating one particle in an entangled pair. Participants examine whether such acceleration affects the entanglement and conservation of momentum.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants inquire about experiments or applications of momentum entanglement and its implications when one particle is accelerated.
  • It is proposed that accelerating one particle will generally break the entanglement due to the interaction involved.
  • One participant questions whether gravitational acceleration would break entanglement, suggesting it might not involve direct interaction.
  • Another participant suggests that certain transformations might not break entanglement, even if they involve changes in momentum.
  • There is a discussion about the possibility of boosting momentum without breaking entanglement, with references to precessing spins as a similar concept.
  • Some participants express skepticism about the idea that altering one particle's momentum would affect the other, emphasizing that entanglement typically remains intact unless specific conditions are met.
  • The conservation of momentum is discussed, with participants noting that the total momentum of the entangled system remains constant even if one particle's momentum is altered.
  • There are mentions of the lack of experimental references for massive particles in relation to these concepts, with a focus on light as a more studied case.

Areas of Agreement / Disagreement

Participants generally disagree on the implications of accelerating one particle in an entangled pair, with multiple competing views on whether entanglement is preserved under certain conditions. The discussion remains unresolved regarding the specifics of gravitational effects and the nature of interactions that might preserve entanglement.

Contextual Notes

Limitations include the lack of consensus on the effects of different types of acceleration on entanglement and the dependence on specific definitions of interactions and measurements. The discussion also highlights the absence of experimental references for massive particles in this context.

Ostrados
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I rarely hear about momentum entanglement, do you know any experiments/applications for momentum entanglement?

If we do momentum entanglement on 2 particles, and then we accelerate one of the particles, will the other particle slow down to obey conservation of momentum? or entanglement will be destroyed?
 
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Ostrados said:
If we do momentum entanglement on 2 particles, and then we accelerate one of the particles, will the other particle slow down to obey conservation of momentum? or entanglement will be destroyed?
No. Whatever interaction is involved in accelerating the particle will also break the entanglement.
 
Nugatory said:
No. Whatever interaction is involved in accelerating the particle will also break the entanglement.

What about gravitational acceleration? it will not involve direct interaction with the particle.
 
Last edited:
Nugatory said:
Whatever interaction is involved in accelerating the particle will also break the entanglement.

A very minor quibble, O Nugatory One, and I am probably going to put my foot in my mouth before finishing... :smile:

If that interaction has the effect of being an irreversible measurement, then of course you are correct. However, there are transforms that don't have that effect. And those do not break entanglement.

Frequency entangled photons (essentially momentum entangled) can move through fiber, changing their direction. They can even have their frequency modified (boosted for example) without breaking their entanglement. As long as no information is gained about their momentum.

I assume similar transforms could occur with electrons.
 
Ostrados said:
What about gravitational acceleration?

This is an open question. Quantum gravity would imply that there might be an effect (however small). Otherwise, it should not.
 
DrChinese said:
If that interaction has the effect of being an irreversible measurement, then of course you are correct. However, there are transforms that don't have that effect. And those do not break entanglement.
Indeed there are... But I am having trouble imagining one that would could be said to "accelerate the particle" in the sense that the OP is thinking about (that is, we know that the result of a momentum measurement after the interaction will be different than before) without breaking the entanglement. That may be a failure of imagination on my part.

In any case OP's line of thought, that we can "slow down" the other particle seems completely illegitimate. "Slow down" implies that the other particle had some (counterfactual) velocity that we've reduced by our interaction with the first particle.
 
Nugatory said:
I am having trouble imagining one that would could be said to "accelerate the particle" in the sense that the OP is thinking about (that is, we know that the result of a momentum measurement after the interaction will be different than before) without breaking the entanglement.

You should be able to boost the momentum of a particle without breaking entanglement. We can precess spins with a magnetic field without breaking their entanglement and it's basically the same idea I think.

It's actually an interesting exercise to figure out why the boosting/precessing doesn't necessarily measure the momentum or spin, despite momentum conservation / angular momentum conservation requiring that some external system be pushed in the opposite direction.
 
So let's say we used 2 electrons, and the speed of the 2nd electron was boosted without breaking the entanglement (which as I understood from the comments is possible), what will happen to the 1st electron? will it slow down?
 
  • #10
Ostrados said:
So let's say we used 2 electrons, and the speed of the 2nd electron was boosted without breaking the entanglement (which as I understood from the comments is possible), what will happen to the 1st electron? will it slow down?

Definitely not. Under no scenario that has been discussed above - which is the exception and not the rule - will doing something to A's momentum cause a related change in B's momentum. The question above is only whether there can be alterations to A's momentum that do NOT break the momentum entanglement with B.
 
  • #11
DrChinese said:
Definitely not. Under no scenario that has been discussed above - which is the exception and not the rule - will doing something to A's momentum cause a related change in B's momentum. The question above is only whether there can be alterations to A's momentum that do NOT break the momentum entanglement with B.

But my question was about momentum entanglement
 
  • #12
Ostrados said:
But my question was about momentum entanglement

And the answer is: accelerating A does not decelerate B in any related manner. It would normally break the entanglement with B (as Nugatory said), but there are occasions which it might not. Gravity would not break entanglement, unless it is a quantum force.
 
  • #13
DrChinese said:
And the answer is: accelerating A does not decelerate B in any related manner. It would normally break the entanglement with B (as Nugatory said), but there are occasions which it might not. Gravity would not break entanglement, unless it is a quantum force.
What about conservation of momentum why it will not hold (in case entanglement was not broken)?
 
  • #14
There is conservation of momentum. Entangled A+B is a constant prior to any acceleration X acting on A. After including X, you have (A+X) +B. Conservation holds.
 
  • #15
DrChinese said:
There is conservation of momentum. Entangled A+B is a constant prior to any acceleration X acting on A. After including X, you have (A+X) +B. Conservation holds.
Ok. So what you are saying in other words is that any added momentum for one of the particles will add to the total momentum of the entanglement system and momentum will be conserved with this new value.

So if we have pA+pB= p and we added x momentum to A then that is equivalent to saying pA+pB = p+x

Its interesting that we can manipulate the total entanglement state without breaking the entanglement.
 
  • #16
Ostrados said:
Its interesting that we can manipulate the total entanglement state without breaking the entanglement.

Yes, and again there are caveats around that. I don't know of any good experimental references for that for particles with mass - only for light. But I believe the theory is the same.
 

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