Quantum Spin: Forgetting, Entanglement & Change

In summary, when measuring an electron's spin on two different axes, the first measurement "forgets" the spin on the first axis and the second measurement gives a different result. This also applies to entangled particles, where measuring one particle affects the other, breaking the entanglement and giving correlated results. Further measurements on the first particle will not provide any new information about the second particle.
  • #1
Xori
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My understanding is that when you measure an electron's spin on on Axis A, and then on Axis B, the spin on Axis A is "forgotten" and can be something different next time you measure it. Is this correct?

If it is, then how does this work across entanglement? If you measure electron A's spin at Axis A, then you know electron B's spin is the opposite. But if you then measure electron's A spin again on Axis B, you can potentially "change" electron B's spin on Axis A?
 
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  • #2
Who says that would "change" the other electron?

If A and B were entangled, measuring A once will give you information about both A and B. It will also generally break the entanglement, so further measurements of A tell you nothing further about B.

For example, if you made a third measurement of A (on axis A for the second time, giving a random result) and then measured B, you would find it correlated with the first (rather than third) measurement of A.
 
  • #3
Damn, now I got to think of another way to communicate FTL.
 
  • #4
Good luck with that.
 
  • #5
Xori said:
My understanding is that when you measure an electron's spin on on Axis A, and then on Axis B, the spin on Axis A is "forgotten" and can be something different next time you measure it. Is this correct?
Have a clear answer for the first part: after the mesurement of spin along the B axis the particle will be in an eigenstate of spin pojected on B. Unless A and B are collinear, this is not an eigenstate of spin projected on A, thus if we make a third measuremnet (aling A again), the probability distribution will no longer be a Kronicker-delta
 

1. What is quantum spin?

Quantum spin is an intrinsic property of particles, such as electrons and protons, that describes their angular momentum and orientation in space. It is one of the fundamental properties of quantum mechanics and plays a crucial role in understanding the behavior of particles at the atomic and subatomic level.

2. How does quantum spin lead to forgetting?

Quantum spin plays a role in the phenomenon of forgetting in quantum systems. When a system is in a state of superposition, meaning it exists in multiple states simultaneously, the quantum spin of the particles in the system becomes entangled with the environment. This leads to a loss of information about the state of the system, resulting in forgetting.

3. What is entanglement in regards to quantum spin?

Entanglement is a phenomenon in which the quantum spin of particles becomes correlated with each other, even when they are physically separated. This means that the state of one particle cannot be described without also describing the state of the other particle. Entanglement plays a key role in quantum spin and is essential for technologies such as quantum computing.

4. Can quantum spin change?

Yes, quantum spin can change. In quantum mechanics, particles can have their spin in any direction, but it is only when we measure the spin that it takes a definite value. This means that the spin can change depending on the measurement and the state of the system at that time.

5. How does quantum spin impact technology?

Quantum spin has a significant impact on technology, particularly in the field of quantum computing. The ability to manipulate and control the state of quantum spin in particles allows for the creation of qubits, the basic unit of quantum computing. This technology has the potential to revolutionize computing and lead to faster and more powerful computers in the future.

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