In an electron double slit experiment, let's put two charged plates behind the slits in an attempt to move the pattern up and down on the the screen.
What will happen? Will it just shift the interference pattern on the screen or washes it out completely?
If it washes it out, what's the minimal field that doesn't affect the pattern? Since I don't believe the electron double slit experiment was performed in an environment where all fields were exactly zero, but they still managed to get the pattern.