  Tests of quantum properties of fundamental particles in high energy colliders
are starting to appear. However, such experiments may suffer from the locality
loophole. We argue for criteria that take into account the space-like
separation between measurements for the case of spin correlations in top quark
pairs produced at the LHC. We derive bounds considering three different
definitions of what constitutes the quantum measurement - the decay of top
quarks, the decay of W bosons, and the stable decay products contacting a
macroscopic device.
