B Is it possible to change a fundamental property of a particle?

Is it possible to change a fundamental property of a particle?
If that can be done, will it's twin particle's state also be altered accordingly?

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haushofer

What exactly do you mean by "changing a fundamental property"?

What exactly do you mean by "changing a fundamental property"?
Something like changing the spin?

Mentor

PeterDonis

Mentor
Something like changing the spin?
Changing what about the spin? Its magnitude or direction?

What "twin particle"?
If two entangled particles are produced, let's take one of them to be the twin of the other.

Excuse me if I didn't get the terms right. I am new to this topic and this forum

Changing what about the spin? Its magnitude or direction?
Direction.

PeterDonis

Mentor
If two entangled particles are produced, let's take one of them to be the twin of the other.
That's not really correct, since nothing requires the two particles to be of the same type.

Direction.
How are you going to change the direction of spin of one of the particles? Is it something that will also affect the other particle? Or are you arranging things so the particles are far enough apart that you can just act on one of them?

Or are you arranging things so the particles are far enough apart that you can just act on one of them?
Yes. That is the case.

DrChinese

Gold Member
Yes. That is the case.
In the situation you describe, there are 2 types of transformations you can do on Alice's entangled particle (one "twin").

1. An irreversible measurement. Bob's particle will now be in a state consistent with the outcome of the measurement on Alice's particle (assuming an irreversible measurement has not already been performed by Bob). Note that the actual result of Alice's measurement is RANDOM.

2. A reversible operation on Alice's particle. This will have no effect on Bob's particle.

1. An irreversible measurement. Bob's particle will now be in a state consistent with the outcome of the measurement on Alice's particle (assuming an irreversible measurement has not already been performed by Bob).
So does that mean if an irreversible measurement is made on Alice's particle and it is found to have a clockwise spin, does Bob's particle have an anti clockwise one (again, assuming an irreversible measurement has not been performed by Bob) ?
I didn't quite get what consistent means here.

DrChinese

Gold Member
So does that mean if an irreversible measurement is made on Alice's particle and it is found to have a clockwise spin, does Bob's particle have an anti clockwise one (again, assuming an irreversible measurement has not been performed by Bob) ?
I didn't quite get what consistent means here.
It depends on the type of entanglement. Much entanglement is anti-correlated (opposite values), due to conservation principles. However, there are also cases where the entanglement is correlated. And other cases where the sum of 2 values will equal a constant, which is again due to conservation.

• StevieTNZ

If it is selecting whether, for example, the spin is up or down, the result is random, but in accordance with what states are possible by the fundamental Schrodinger equation.

• It depends on the type of entanglement. Much entanglement is anti-correlated (opposite values), due to conservation principles. However, there are also cases where the entanglement is correlated. And other cases where the sum of 2 values will equal a constant, which is again due to conservation.
Fine. Thanks a lot.

• bhobba

FX_physics

two particle are entangle or not was decided at the moment when it was created. Such as an electron downward transition twice can create two photon with spin opposite entanglement.

DrClaude

Mentor
two particle are entangle or not was decided at the moment when it was created.
That's not correct. Generally speaking, any time particles interact, they can become entangled.

• vanhees71

"Is it possible to change a fundamental property of a particle?"

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