How is spooky action at a distance measured? My recent background reading: https://www.science.org/content/article/more-evidence-support-quantum-theory-s-spooky-action-distance
I have been trying to understand how experiments actually measure the state of both entangled electrons. The way it is typically explained is that one measures the first entangled electron, and according to the Heisenberg Uncertainty Principle it's state is now resolved. Since it is entangled with the other electron, the other one is also implied to share the same state. But how does one simultaneously measure the other entangled electron to determine that it's state is indeed the same as the other electron? What is the mechanism by which that measurement is made, which allows one to confirm that the other electron actually shares the same state in that instance in time?
 A: In general, for entangled spin pairs magnetic fields are used.
But it's important to note that the states are not the same, as you have stated, but are actually anticorrelated.
So for two entangled electrons, measuring spin along a particular axis, one of them may have a spin "up"  and its entangled partner will have a spin "down", the anticorrelated value. Magnetic fields can allow us to measure  this.
The Stern-Gerlach$^1$ setup to measure how particles behave in a magnetic field is summarized here. Electrons (and other particles with spin) have a magnetic dipole moment and how they interact with magnetic fields tells us about their spin orientation. Imagine the electron as being a tiny magnetic dipole or "bar magnet", and then imagine what happens if this little magnet is moving in a larger surrounding magnetic field, and how the forces on this magnet would operate depending on the orientation of this magnet (or its direction of spin). Think about one of the electrons moving through one setup and the other through a similar setup in the opposite direction a certain distance away.
Even though both setups may have a spacelike separation, both measurements will come up anticorrelated. And if one is measured before the other, the same will apply even though both electrons are inititally in a superposition of both the up and down state prior to measurement. The initial conclusion was that measuring one state instantaneously "causes" the entangled partner to then be in the anticorelated state, though care must be taken since correlation and causation are not the same thing.
$^1$Note the part that talks about single electrons since the original experiment used silver atoms with an unpaired outer electron, and the results described the spin of this electron.
