Subdecoherent information encoding in a quantum-dot array

A potential implementation of quantum-information schemes in semiconductor nanostructures is studied. To this end, the formal theory of quantum encodi ng for avoiding errors is recalled and the existence of noiseless states fo r model systems is discussed. Based on this theoretical framework, we analy ze the possibility of designing noiseless quantum codes in realistic semico nductor structures. In the specific implementation considered, information is encoded in the lowest energy sector of charge excitations of a linear ar ray of quantum dots. The decoherence channel considered is electron-phonon coupling We show that besides the well-known phonon bottleneck, reducing si ngle-qubit decoherence, suitable many-qubit initial preparation, as well as register design may enhance the decoherence time by several orders of magn itude. This behavior stems from the effective one-dimensional character of the phononic environment in the relevant region of physical parameters. [S0 163-1829(99)07607-9].