  If black holes are not to be dreaded syncs of information but be fully
described by unitary evolution, they must scramble in-falling data and
eventually leak it through Hawking radiation. Sekino and Susskind have
conjectured that black holes are fast scramblers: they generate entanglement at
a remarkably efficient rate, with characteristic time scaling logarithmically
with the entropy. In this work, we focus on Matrix theory -- M theory in the
light-cone frame -- and directly probe the conjecture. We develop a concrete
test bed for quantum gravity using the fermionic variables of Matrix theory and
show that the problem becomes that of chains of qubits with an intricate
network of interactions. We demonstrate that the black hole system evolves much
like a Brownian quantum circuit, with strong indications that it is indeed a
fast scrambler. We also analyze the Berenstein-Maldacena-Nastase model and
reach the same tentative conclusion.
