The January Philosophy Book of the Month 2019 is The Runaway Species. Discuss The Runaway Species now.

The February Philosophy Book of the Month is The Fourth Age by Byron Reese (Nominated by RJG.) Discuss The Fourth Age now.

Would this thought experiment prove or disprove Quantum randomness?

Use this forum to discuss the philosophy of science. Philosophy of science deals with the assumptions, foundations, and implications of science.
Post Reply
User avatar
john taylor
New Trial Member
Posts: 1
Joined: October 31st, 2018, 6:59 pm

Would this thought experiment prove or disprove Quantum randomness?

Post by john taylor » October 31st, 2018, 7:07 pm

I was told of a thought experiment by a friend of mine who says that his thought experiment will either prove or disprove randomness in quantum mechanics, and this was in fact verified by several other physicists, who said that if this experiment was ever successfully carried out it would either prove or disprove quantum randomness.

His thought experiment imagines (in laymans terms), two teams of scientists who want to measure the position of 10 000 neutrons which will be fired, so that they travel 1 at a time. The scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers.

Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randomly collapsing 100% (all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process (because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath), however the only way for randmness to then be proven would be for the scientists to observe to conflicting results for the same particle at exactly the same time, for it's position, because it was shown earlier that it would not be random for two random relative processes(the collapse of the wave function), to yield the same result for the position of a large sample of particles, so the only way to disprove this would be to observe an instance in which tow conflicting results for the position of a particle is measured at exactly the same time.

Would this experiment be a proof if it could be done? or do you think that the experiment is a stepping stone to another experiment which might work? (my friend added that it is a thought experiment because it is impossible to measure something at exactly the same time, furthermore he said that invoking Heisenberg's uncertainty principle as an objection is not valid, because it is not about obtaining results for its original position but its position)

User avatar
Halc
Posts: 294
Joined: March 17th, 2018, 9:47 pm

Re: Would this thought experiment prove or disprove Quantum randomness?

Post by Halc » November 1st, 2018, 7:41 am

john taylor wrote:
October 31st, 2018, 7:07 pm
I was told of a thought experiment by a friend of mine who says that his thought experiment will either prove or disprove randomness in quantum mechanics, and this was in fact verified by several other physicists, who said that if this experiment was ever successfully carried out it would either prove or disprove quantum randomness.
You're probably going to have to explain what this 'quantum randomness' is that you're disproving. I'll try to figure it out, but somehow I doubt you have a way to disprove something like predictions only being expressible as probabilities.
His thought experiment imagines (in laymans terms), two teams of scientists who want to measure the position of 10 000 neutrons which will be fired, so that they travel 1 at a time. The scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time.
How are they going to do that? You send a neutron into a bath of gamma rays, and some rays bounce off it, sending the neutron on an erratic course. Each gamma ray deflected in this process hits a sensor of one team or the other, so there will be no 'at the same time' about it. If the two teams share sensors, they are essentially the same team.
You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers.
This is more easily done by measuring entangled particles. The wave function is identical to the two teams, and nobody can predict any better, but their measurements are effectively 'at the same time' even if done widely separated. So in both cases (the thought experiments and entanglement), the measurements, if done actually at the same time, will be found to be correlated. This does work 100% of the time for entanglement, and it doesn't prove determinism any more than your thought experiment. It all depends on your interpretation of QM.
Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randomly collapsing 100% (all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process
Funny definition you have then. I flip a coin and two parties always agree on it coming up heads or tails, therefore a coin flip is not a random process. By definition, it is deterministic (not random) if you can predict the outcome before it is measured, not if two measurements agree all the time. The latter only proves correlation, which is still indeterminate.

User avatar
Halc
Posts: 294
Joined: March 17th, 2018, 9:47 pm

Re: Would this thought experiment prove or disprove Quantum randomness?

Post by Halc » November 1st, 2018, 8:19 am

For that matter, I've not heard of using gamma rays for neutron position detection. Usually they send the neutron into some sensitive material like helium-3 and look for the byproducts of the reaction. This detects existence of neutrons, but I suppose isn't very good an taking a measurement of the position of the thing. It is unclear how one might actually go about doing that. What does a neutron/gamma-ray interaction do to both particles? How is that subsequently measured by the physicist such that position might be gleaned from it? I mean, all you get is the fact that a ray hits a sensor over here at time T. Does that tell you where the interaction took place?

User avatar
LuckyR
Moderator
Posts: 3284
Joined: January 18th, 2015, 1:16 am

Re: Would this thought experiment prove or disprove Quantum randomness?

Post by LuckyR » November 2nd, 2018, 2:27 am

john taylor wrote:
October 31st, 2018, 7:07 pm
I was told of a thought experiment by a friend of mine who says that his thought experiment will either prove or disprove randomness in quantum mechanics, and this was in fact verified by several other physicists, who said that if this experiment was ever successfully carried out it would either prove or disprove quantum randomness.

His thought experiment imagines (in laymans terms), two teams of scientists who want to measure the position of 10 000 neutrons which will be fired, so that they travel 1 at a time. The scientists will measure the position of these neutrons by bouncing gamma rays off of the neutron to find its location, and they will measure it at exactly the same time. You would naturally expect both parties to measure the exact same position each time for each particle. However because the probability of the wave function is relative to each observer, the wave function collapse would have to collapse randomly relative to each of the two observers.

Therefore if they observe the same location for each neutron 100% of the time it would prove determinism because if the wave function is randomly collapsing 100% (all of the time) of the time to produce the same result for its location for both observers it is by definition not a random process (because you cannot consistently get the same result from two random process all of the time, that would suggest if this took place that it was not random but that it was fixed and that there was a defined process taking place underneath), however the only way for randmness to then be proven would be for the scientists to observe to conflicting results for the same particle at exactly the same time, for it's position, because it was shown earlier that it would not be random for two random relative processes(the collapse of the wave function), to yield the same result for the position of a large sample of particles, so the only way to disprove this would be to observe an instance in which tow conflicting results for the position of a particle is measured at exactly the same time.

Would this experiment be a proof if it could be done? or do you think that the experiment is a stepping stone to another experiment which might work? (my friend added that it is a thought experiment because it is impossible to measure something at exactly the same time, furthermore he said that invoking Heisenberg's uncertainty principle as an objection is not valid, because it is not about obtaining results for its original position but its position)
There is a difference between "random" and "unpredictable"
"As usual... it depends."

Post Reply