Hacker News Reader

Comment by kurthr | Hacker News Reader

So to be simple you're saying the field is the slope (or actually gradient) of the potential. So if it's constant (but high) there is no slope, but significant potential, like being on a mesa. And that difference in potential rather than slope affects the paired quantum particles?

View on HN

Kinda. The magnetic field is the curl of the vector potential. If the vector potential is nonzero but curl-less then you get zero magnetic field, but the particles’ wavefunctions still feel the vector potential.

(Specifically, the phase of the wavefunction is affected; obviously nothing observable about a single wavefunction could be affected in the absence of a field, via the correspondence principle. But when you have two electrons, that phase difference does show up in their interference pattern.)

I think I understand the Aharonov–Bohm effect for magnetism, but I don't understand how you can have the branches at different gravitational potentials without the packets experiencing a field somewhere when they branch/join.

I'm trying to figure out how gravity has curl?

It's not the electric field; it's the magnetic field. There is still a potential, but the potential is a vector.

My ability to picture what is going on has never extended to the magnetic vector potential, so I have no intuition about how that plays in here...

There is an electrical variant of the effect, it just hasn't been well tested experimentally.

Right, but pairs of particles aren't relevant. The effect occurs for any particle that interacts electromagnetically. And the magnetic field is the curl of its potential.

Reply on news.ycombinator.com