  Controllable systems relying on quantum behavior to simulate distinctly
quantum models so far rely on increasingly challenging classical computing to
verify their results. We develop a general protocol for confirming that an
arbitrary many-body system, such as a quantum simulator, can entangle distant
objects. The protocol verifies that distant qubits interacting separately with
the system can become mutually entangled, and therefore serves as a local test
that excitations of the system can create non-local quantum correlations. We
derive an inequality analogous to Bell's inequality which can only be violated
through entanglement between distant sites of the many-body system. Although
our protocol is applicable to general many-body systems, it requires finding
system-dependent local operations to violate the inequality. A specific example
in quantum magnetism is presented.
