We numerically investigate the minimum number of interacting particles,
which is required for the onset of strong chaos in quantum systems
on a one-dimensional lattice with short-range and long-range interactions.
We consider multiple system sizes which are at least three times larger
than the number of particles and find that robust signatures of quantum
chaos emerge for as few as 4 particles in the case of short-range
interactions and as few as 3 particles for long-range interactions,
and without any apparent dependence on the size of the system.
Entanglement growth in many-body localized systems with long-range interactions
