Preparation and addressability of molecular vibrational qubit states in the presence of anharmonic resonance

Recently, our group has exemplified the possibility of quantum computing with molecular vibrations in a 2D model of acetylene. Specially shaped fs-laser pulses in the IR-regime represent the global quantum gates and can be acquired by optimal control theory. With regard to leakage from the qubit basis used for quantum computation, the influence of dark, non-IR-active modes coupled via anharmonic resonances is an important issue. In a 3D model we demonstrate the selective preparation of a vibrational eigenstate in near anharmonic resonance. Furthermore, a Hadamard gate is realized, the first step in the preparation of a Bell state, also demonstrated. (C) 2003 Elsevier B.V. All rights reserved.