  We study quantum information properties of a seven-level system realized by a
particle in an one-dimensional square-well trap. Features of encodings of
seven-level systems in a form of three-qubit or qubit-qutrit systems are
discussed. We use the three-qubit encoding of the system in order to
investigate subadditivity and strong subadditivity conditions for the thermal
state of the particle. The qubit-qutrit encoding is employed to suggest a
single qudit algorithm for calculation of parity of a bit string. Obtained
results indicate on the potential resource of multilevel systems for
realization of quantum information processing.
