Meaning of velocity in Bohm interpretation

[Gerenuk]

In the Bohm interpretation particles have a definite position and also a velocity?

How is this velocity related to velocities and momenta in the Copenhagen interpretation of QM?

[Demystifier]

In general, this velocity/momentum is completely different than that in the Copenhagen interpretation (CI).
However, in a special case in which the velocity/momentum is MEASURED, then it becomes identical to that in CI.
Bohm interpretation describes (or at least attempts to describe) what exactly happens during the measurement, as well as what exactly happens when the measurement is not performed.

[Gerenuk]

Thanks for the clarification.
Do you mean if I set up a momentum measuring device at one point, it would measure the "classical Bohm" velocity?

How then would you describe the difference between momentum in B and CI? Do you mean I cannot take the momentum from B and construct the wavefunction from it?

[Demystifier]

Do you mean if I set up a momentum measuring device at one point, it would measure the "classical Bohm" velocity?

If the measuring device is constructed such that it measures the velocity, then this device measures the "classical" Bohm velocity. However, such a measuring device does not measure the position of the particle, even though the particle has a definite position too.


Do you mean I cannot take the momentum from B and construct the wavefunction from it?
In general, that is correct. The exception is the case in which you have measured the momentum, in which case you can construct the wave function from knowledge of the momentum.