A dinitro[1,3]anthracene molecule is shown to perform an half adder logic function with no resemblance to the topology of an electronic circuit performing the same function. The logic function is obtained by the control of the molecule quantum trajectory in its molecular orbitals electronic quantum state space by changing the conformation of the NO2 groups, starting from an initial non-stationary state independent of the input configuration. Time dependent quantum interference effects controlled by the relative position and degeneracy of the molecule eigenstates is at the origin of this half adder logic gate. (c) 2005 Elsevier B.V. All rights reserved.