Quantum Entanglement: Changes at E1 & E3 Affecting Particle A

In summary, the conversation discusses quantum entanglement and its effects on particles. The question of when a particle's spin changes is deemed meaningless according to the theory of special relativity. The concept of "now" also has no physical meaning in this context. The scenario also highlights the limitations of the interpretation of QM that suggests an instantaneous change in one particle's properties affecting the other entangled particle.
  • #1
Stephanus
1,316
104
Dear PF Forum,
I have a question regarding Quantum Entanglement.
QE.JPG

I don't know much about QE, but there's something that I want to know.
Two particles are entangled.
Blue line is the world line of Particle A

See Pic 02
Particle B travels according to Green line.
And at E1 Particle B's spin is changed (is that how we say it in QM?) so the "change" is reflected in Particle A, right.
A: Is it true that E1's "now" is at E2, according to SR?

Now Particle B accelerates a little so its word line is the Red Line. See Pic 02
And at E3 Particle B's spin is changed, now the change (Pic 03) is reflected at E2
B: Is it true that E3's "now" is at E2 ,according to SR?

C: Can, at E2, particle A is changed according to two different events?

Thank you very much
 
Physics news on Phys.org
  • #2
The "event" would properly be the event that the spin was measured.
 
  • Like
Likes Stephanus
  • #3
Stephanus said:
And at E1 Particle B's spin is changed (is that how we say it in QM?) so the "change" is reflected in Particle A, right.

The usual way would be to say that a measurement is made of particle B's spin, which, at least according to some interpretations of QM, forces particle A's spin to change "instantaneously". But no measurement is being made of particle A's spin, so the question of "when" particle A's spin changes is physically meaningless--indeed, the claim that "particle A's spin changes" is itself physically meaningless.

Stephanus said:
Is it true that E1's "now" is at E2, according to SR?

No. SR says that the concept of "now" has no physical meaning.

Stephanus said:
at E3 Particle B's spin is changed, now the change (Pic 03) is reflected at E2

No; particle B's spin is measured a second time, but just as above, since no measurement is being made of particle A's spin, the question of "when" particle A's spin changes is physically meaningless, as is, indeed, the claim that particle A's spin "changes" at all.

There is also another factor you are overlooking: even on the interpretations of QM where the first measurement of particle B's spin "changes" particle A's spin "instantaneously", via entanglement, that process also breaks the entanglement. So on this interpretation, when the second measurement of particle B's spin is made, it no longer does anything to particle A's spin because the two are no longer entangled.

Stephanus said:
Is it true that E3's "now" is at E2 ,according to SR?

No. See above.

Stephanus said:
Can, at E2, particle A is changed according to two different events?

No. See above.

What this scenario is really illustrating is the limitations of the interpretation of QM that says that a measurement of one entangled particle "instantaneously" changes a property of the other entangled particle. The best way to deal with this is to drop that interpretation.
 
  • Like
Likes Stephanus

What is quantum entanglement?

Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become connected in such a way that the state of one particle is dependent on the state of the other, even at great distances.

How does quantum entanglement work?

Quantum entanglement occurs when two or more particles are created in such a way that their properties are dependent on each other. This means that any change in the state of one particle will result in a change in the state of the other particle, regardless of how far apart they are.

What is E1 and E3 in relation to quantum entanglement?

E1 and E3 refer to energy levels in a quantum system. These energy levels can affect the entanglement between particles, as changes in energy can alter the entangled state of the particles.

How does a change at E1 or E3 affect particles in quantum entanglement?

A change in energy at E1 or E3 can cause a change in the entangled state of particles. This means that a change in one particle's energy level can result in a change in the other particle's energy level, even if they are separated by a great distance.

What are the potential applications of quantum entanglement?

Quantum entanglement has potential applications in quantum computing, cryptography, and secure communication. It also has implications for our understanding of the fundamental laws of nature and can be used in experiments to test quantum mechanics.

Similar threads

  • Special and General Relativity
2
Replies
40
Views
2K
  • Quantum Physics
Replies
4
Views
735
Replies
41
Views
2K
Replies
24
Views
1K
Replies
33
Views
2K
  • Quantum Physics
Replies
8
Views
652
  • Quantum Interpretations and Foundations
3
Replies
79
Views
5K
  • Special and General Relativity
Replies
9
Views
1K
  • Special and General Relativity
Replies
17
Views
3K
  • Quantum Interpretations and Foundations
2
Replies
37
Views
1K
Back
Top