I don't know how they did it, but verifying Bells inequality would do it if you made many pairs

I'm under the impression you can't. You create an environment that is more likely to keep the sets of particles from interacting with anything else and then you create an entangled pair. To confirm the entanglement I believe would take several measurements of several pairs of particles and these measurements would result in a probability that they were still entangled, not a certainty.

I found this explanation:

https://www.quora.com/Is-it-possible-to-detect-if-a-particle...

In my opinion, it's not the entanglement that is interesting or confusing, it's the super positions of both particles before they are measured that is hard to explain... How can two particles be in super positions of two states but then when you measure them they are always complimentary? Either it was "spooky action at a distance" ie (particle A communicated it's measurement result to particle B) or there is "hidden variables" inside the super positions that determines the result of the measurements.

Easy-peasy. They will periodically see if the photons, when measured had already been measured by an eavesdropper. In quantum world measurement will affect the entangled system, so it’s impossible for someone to measure (read) the data in between without it being detected at both ends.

Check correlation via interference. They'll give consistent results if entangled, and random results if they're not.

Perhaps by checking their Instagram status.