  The efficient experimental verification of entanglement requires an
identification of the essential physical properties that distinguish entangled
states from non-entangled states. Since the most characteristic feature of
entanglement is the extreme precision of correlations between spatially
separated systems, we propose a quantitative criterion based on local
uncertainty relations (quant-ph/0212090). Some basic sum uncertainty relations
for N-level systems are introduced and the amount of entanglement that can be
verified by violations of the corresponding local uncertainty limit is
discussed.
