While a full quantum treatment of gravitation presents many unsolved theoretical challenges, at low energies and metric curvatures, many of these problems can be ignored and an effective quantum gravitational field-theory can be obtained as a perturbation to the classical solutions. However, there has yet to be an experimental test confirming the need for a quantum treatment of gravity. Simply put, does a gravitational source in a quantum superposition state lead to a quantum-valued space-time metric, or does our normal intuition of quantum physics break down when applied to gravitational systems? While the quantum signatures of gravity are expected to be very small, it was recently shown that they should be observable with modest improvement in current experimental techniques. To comprehensively test for such tenuous effects will require the full power of quantum metrology. For example, it can be shown that quantum and classical signatures of gravity can be discriminated when the appropriate measurements are made, if a very specific quantum probe state can be prepared.