Basically they get to measure a super position particle twice, by using an entangled pair of it. So two detectors that each measure one of the particle's 3 possible spin directions, which are known to be identical (but usually you only get to make 1 measurement, so now we can essentially measure 2 directions). We then compare how the different spin directions agree or disagree with each other in a chart.
15% of the time they get combination result A, 15% of the time they get combination result B. Logically we would expect a result of A or B 30% of the time, and combination result C 70% of the time (There are only 3 combinatorial output possibilities - A,B,C)
But when we set the detectors to rule out result C (so they must be either A or B), we get a result of 50%.
So it seems like the particle is able to change it's result based on how you deduce it. A local hidden variable almost certainly would be static regardless of how you determine it.
This is simplified and dumbified because I am no expert, but that is the gist of it.
15% of the time they get combination result A, 15% of the time they get combination result B. Logically we would expect a result of A or B 30% of the time, and combination result C 70% of the time (There are only 3 combinatorial output possibilities - A,B,C)
But when we set the detectors to rule out result C (so they must be either A or B), we get a result of 50%.
So it seems like the particle is able to change it's result based on how you deduce it. A local hidden variable almost certainly would be static regardless of how you determine it.
This is simplified and dumbified because I am no expert, but that is the gist of it.