Our preliminary results strongly hint that quantum dynamics may present at very low temperatures with energy transfer between 0.08 and 0.44 meV in classical dipolar spin ice Dy2Ti2O7. Encouraged by this, we propose to carry out comprehensive inelastic neutron scattering experiments on a unique isotope-enriched high quality Dy2Ti2O7 single crystal at both IN5 and IN12. We request 7 days of beam time at IN5 to map out possible spin excitations in a wide area of energy and momentum space. At IN12, we will carefully measure possible spin-space anisotropy of quantum excitation that has been identified in prior at IN5 with polarized inelastic scattering. Based on our previous experience, we request 7 days of measurement at IN12. We believe that regardless of a positive or a negative result, the proposed experiments can help to clarify one of the most hotly debated issues in condensed matter physics.