The phenomenon we are trying to explain is the interference pattern seen when you send a stream of particles through a double slit (barrier with 2 slits) apparatus. As long as you do not make any measurement, you ALWAYS get an interference pattern. EVEN if you send ONE electron at a time through the double slit apparatus, you STILL see an interference pattern. This is the part where Copenhagen interpretation says – the electron effectively seems to go through BOTH holes….when you don’t try and measure it.
The Pilot Wave
Think of a PILOT WAVE as a wave on an ocean surface. Think of an electron as a piece of debris (say a soda can) floating on the wave. The motion of the soda-can is GUIDED entirely by the underlying wave. It has no independent motion of its own.
Now – place two slits (a barrier with 2 slits) in front of this wave with the can of soda. The soda can WILL, in reality, pass through ONLY ONE Slit. It cannot pass through BOTH (as inferred in the standard Copenhagen interpretation).
The pilot wave, however, passes through both slits. The end result of this is that you get the interference pattern one sees in standard quantum mechanics. Not due to the particle interfering with itself – but due to the pilot wave – behaving like a normal wave does (interferes with itself).
MEASURING a particle, causes the PILOT wave to collapse, revealing the position of the electron. This is equivalent to the ocean wave suddenly evaporating – the soda can will be made immediately OBSERVABLE.
Why is it not a popular interpretation of QM?
It is not popular with physicists because it predicts certain non-local (faster than light) effects – which are beyond even the standard ENTANGLEMENT that is part of QM. One has to almost accept instantaneous action at a distance.
Valentini showed that his expansion of the De Broglie–Bohm theory would allow “signal nonlocality” for non-equilibrium cases in which
Valentini furthermore showed that an ensemble of particles with known wave function and known nonequilibrium distribution could be used to perform, on another system, measurements that violate the uncertainty principle.