Is the two slit experiment "measurement device" always symmetric? In this simplified video that is quite famous on youtube, it says that they tried to measure the electron by one slit. That seems to imply that it could be introducing interaction asymmetry in the underlying (higgs and or gravity) field.
Is the same interference pattern measured by single electrons when there is no asymmetry in the measuring architecture/apparatusi? (That is simply speaking, symmetrically, a measurement device by each slit).
And when both the architecture is symmetric, and they put one electron through each slit at once, is the result the same as when they put a single electron through a single slit?
 A: I want to provide some more context from the video: Starting at 3:40, after describing the double-slit experiment resulting in multiple "bright and dark bands on the screen", Dr. Quantum says as follows:

But physicists were completely baffled by this, so they decided to
  peak and see which slit it actually goes through. They put a measuring
  device by one slit to see which one it went through... and let it fly!
  But the quantum world is far more mysterious than they could have
  imagined. When they observed, the electron went back to behaving like a
  little marble. It produced a pattern of two bands, not an interference
  pattern of many! The very act of measuring or observing which slit it
  went through meant: it only went through one, not both!

There is no reason to imply anything besides non-relativistic quantum mechanics, which explains this experiment perfectly.
The explanation for the double-slit experiment as described has the following assumptions/approximations:


*

*All the electrons act like single electrons (i.e. no interaction), at least qualitatively.

*They are prepared so that the wave function that approximates them is a plane wave (or a spherical wave at sufficient distance).


This produces the behavior as described in the video, including the scenario with the measuring device by no, one or both slits.
So, to answer your questions specifically:


*

*Yes, a single electron (to be precise: the experiment repeated many times, because a single electron produces only a single "dot" on the detector as it is detected as a particle) produces the same patterns because, as mentioned, the behavior of many electrons is actually well-approximated by the behavior of a single electron in this particular experiment. So, spatial symmetry of the experimental setup is of no relevance as long as the electrons fulfill the above approximation.

*Putting one electron through each slit would require an experimental setup that can do that, i.e. preparing the two electrons so that they travel separately from the two emitter devices to their respective slit. Then, the wave function of each electron is not a plane or spherical wave any more. It is localized, at least so that the wave functions of the two electrons don't overlap. The behavior of each electron-slit-combination can be calculated separately, and they act like the other combination just doesn't exist in very good approximation. So it's just two single-slit experiments next to each other.


I think an intuitive explanation for the latter experiment is that, by preparing the electrons to be localized, you "observe" them as being localized in a similar way as the measuring devices. Mathematically, both scenarios impose boundary conditions to the wave functions (i.e. it has to be zero in some portions of the experiment).
