Understanding Bohmian Mechanics of Instrumentalists

[Demystifier]

@Demystifier
Another question just occurred to me: is there a "measurement problem" with Bohmian Mechanics?

No, Bohmian mechanics is a solution of the measurement problem.

See also my lecture http://thphys.irb.hr/wiki/main/images/e/e6/QFound4.pdf
especially page 24.

 

[Lynch101]

@Demystifier Sabine Hossenfelder just put out a video about Bohmian Mechanics. Any thoughts?

 

[Demystifier]

Any thoughts?

She should read my http://thphys.irb.hr/wiki/main/images/3/3d/QFound5.pdf

 

[Lynch101]

She should read my http://thphys.irb.hr/wiki/main/images/3/3d/QFound5.pdf

Nice one. I'll have a read it myself.

 

[Lynch101]

How does a measurement occur in Bohmian Mechanics? I was thinking that the pilot wave guided the particle towards the detector and once it comes into contact with the detector a measurement is registered (allowing for the internal processes of the measurement apparatus). Is that accurate, or is it possible that a particle can come into contact with a detector but a measurement fail to be registered?

 

[Demystifier]

How does a measurement occur in Bohmian Mechanics? I was thinking that the pilot wave guided the particle towards the detector and once it comes into contact with the detector a measurement is registered (allowing for the internal processes of the measurement apparatus). Is that accurate, or is it possible that a particle can come into contact with a detector but a measurement fail to be registered?

It's not accurate because it's not clear what do you mean by "comes into contact". Do you mean that particles come into contact, or that wave functions come into contact? Does "coming into contact" mean they arrive at the same place and touch each other, or just that they influence each other? Have in mind that particles interact non-locally in BM, so particles don't need to arrive at the same place to influence each other.

 

[martinbn]

It's not accurate because it's not clear what do you mean by "comes into contact". Do you mean that particles come into contact, or that wave functions come into contact? Does "coming into contact" mean they arrive at the same place and touch each other, or just that they influence each other? Have in mind that particles interact non-locally in BM, so particles don't need to arrive at the same place to influence each other.

Don't want to intrude on your conversation, but what does it mean for the wave functions to come into contact? Also what is meant by the particles influence each other?

 

[Demystifier]

Don't want to intrude on your conversation, but what does it mean for the wave functions to come into contact? Also what is meant by the particles influence each other?

You think that BM is nonsense, so why bother?

 

[martinbn]

You think that BM is nonsense, so why bother?

Can you blame me? Every Bohmian mechanic gives me such answers.

 

[Demystifier]

Can you blame me? Every Bohmian mechanic gives me such answers.

I blame you for asking questions you are not really interested in. What do you mean by "such answers"?

 

[Lynch101]

It's not accurate because it's not clear what do you mean by "comes into contact". Do you mean that particles come into contact, or that wave functions come into contact? Does "coming into contact" mean they arrive at the same place and touch each other, or just that they influence each other? Have in mind that particles interact non-locally in BM, so particles don't need to arrive at the same place to influence each other.

I guess I'm just wondering how a measurement occurs in BM.

I had an intuitive idea as to how a measurement occurs. For example, a ball thrown at a wall collides with the wall and leaves a mark. I thought measurements in BM were analogous. The particle is guided by the pilot wave until it collides with the detector (which gets amplified for the purpose of human observation).

Is it the case that a particle which arrives at position A, on the LHS of the detector, can result in a measurement at a position Z on the RHS? For example, in the picture, is it possible for the particle to arrive at the red position but result in the yellow measurement?

 

[Nugatory]

For example, in the picture, is it possible for the particle to arrive at the red position but result in the yellow measurement?

That depends on the design of the lab equipment that does the amplification. If it could behave as you describe we would not use it for experiments involving interference patterns, although it might be perfectly satisfactory as a particle counting device.
(And note that only the Bohmians do not have to wrap the phrase “particle arrives at…” in interpretational disclaimers before they can use it)

 

[Demystifier]

Is it the case that a particle which arrives at position A, on the LHS of the detector, can result in a measurement at a position Z on the RHS? For example, in the picture, is it possible for the particle to arrive at the red position but result in the yellow measurement?

Under certain conditions, something like that is possible. When it happens, one talks about surrealistic Bohmian trajectories, on which you can find more information by googling.

 

[Demystifier]

The particle is guided by the pilot wave until it collides with the detector

The particle is always guided by the pilot wave. Collision with the detector means that pilot wave of the particle gets entangled with pilot wave of the detector, i.e. they form one big pilot wave for the joint system consisting of the particle and the detector (which itself consists of many particles).

 

[Lynch101]

Does the Legget-Garg inequality tell us anything about Bohmian Mechanics, or does it simply not apply?

 

[Demystifier]

Does the Legget-Garg inequality tell us anything about Bohmian Mechanics, or does it simply not apply?

The LG inequality is about temporal correlations. Some people (including @A. Neumaier) were arguing in the past that BM does not correctly reproduce the quantum mechanical temporal correlations. But it is wrong. The measurable temporal correlations in QM are the same as measurable temporal correlations in BM. To understand that, one has to take into account what happens with the wave function at the time of measurement. It gets entangled with the wave function of the detector, which is responsible for an effective (apparent) wave function "collapse". More details can be found in the book F. Laloe, "Do We Really Understand Quantum Mechanics?", Appendix I.

 

[physika]

"'Created' seems to imply that a particle is not the effect of its antecdent state, while a particle that is 'destroyed' wouldn't be "the cause of the state that is to follow". Am I correct in that characterisation of the notions of 'create' and 'destroy'?

Of course, this would be perfectly in-keeping with the notion of an indeterministic interpretation but it would seem to require an incredibly 'extraordinary' explanation. Again, relating it back to the age-old question, how can a particle be created from absolutely nothing? How can something come from absolutely nothing? How can a particle then simply cease to have any properties whatseover?

Good points.

 

[PeterDonis]

Good points.

No, they're not. See post #6.

(When responding to a post that was made quite some time ago, it's a good idea to read the thread first to see if others have already responded to it.)

 

[physika]

In physics it's that each state in a given physical world was always a fact and could never have been differently if you rewind the tape with the same initial conditions.

That is called, Fatalism, a " flavor" of determinism.

...without the need to have read subsequent posts

...

 

[physika]

Even in a timeless universe with no events unfolding, it would still be a complete mystery why things are correlated that show no causal connection.

all already written.

...