  Quantum discord is a prominent measure of quantum correlations, playing an
important role in expanding its horizon beyond entanglement. Here we provide an
operational meaning of (geometric) discord, which quantifies the amount of
non-classical correlation of an arbitrary quantum system in terms of its
minimal distance from the set of classical states, in terms of teleportation
fidelity for general two qubit and $d \otimes d$ dimensional isotropic and
Werner states. A critical value of the discord is found beyond which the two
qubit state must violate the Bell inequality. This is illustrated by an open
system model of a dissipative two qubit. For the $d \otimes d$ dimensional
states the lower bound of discord is shown to be obtainable from an
experimentally measurable witness operator.
