On the (Non)Equivalence of the Schr\"odinger and Heisenberg Pictures of Quantum Mechanics

The aim of this short Note is to show that the Schr\"odinger and Heisenberg pictures of quantum mechanics are not equivalent unless one uses a quantization rule clearly stated by Born and Jordan in their famous 1925 paper. This rule is sufficient and necessary to ensure energy conservation in Heisenberg's matrix mechanics. It follows, in particular, that Schr\"odinger and Heisenberg mechanics are not equivalent if one quantizes observables using the Weyl prescription.