  The Lieb-Robinson bound (LRB) states that the range and strength of
interactions between the constituents of a complex many-body system impose
upper limits to how fast the signal can propagate. It manifests in a light
cone-like growth of correlation function connecting two distant subsystems.
Here we employ the techniques of quantum information to demonstrate that the
LRB can be determined from local measurements performed on a single qubit that
is connected to a many-body system. This formulation provides an operational
recipe for estimating the LRB in complex systems, replacing the measurement of
the correlation function with simple single-particle manipulations. We
demonstrate the potency of this approach by deriving the upper limit to the
speed of signal propagation in the XY spin chain.
