[MAMAMassakali]

From the complementary states of the entangled particles we know entanglement happens. But then how do we know that the collapse and "de-entaglement" happens instantaneously if we can't determine whether superposition collapsed or not?

[Jweb_Guru]

You can't determine it at the exact moment it happens, but you can meet up later (traveling well below the lightspeed limit) and compare notes.