  We study quantum information scrambling in spin models with both long-range
all-to-all and short-range interactions. We argue that a simple global,
spatially homogeneous interaction together with local chaotic dynamics is
sufficient to give rise to fast scrambling, which describes the spread of
quantum information over the entire system in a time that is logarithmic in the
system size. This is illustrated in two tractable models: (1) a random circuit
with Haar random local unitaries and a global interaction and (2) a classical
model of globally coupled non-linear oscillators. We use exact numerics to
provide further evidence by studying the time evolution of an out-of-time-order
correlator and entanglement entropy in spin chains of intermediate sizes. Our
results pave the way towards experimental investigations of fast scrambling and
aspects of quantum gravity with quantum simulators.
