Complex sentence: In quantum information theory, a quantum circuit is a model for quantum computation in which a computation is a sequence of reversible transformations on a quantum mechanical analog of an "n" bit register.
Split into simpler sentences: In quantum information theory, a quantum circuit is a model for quantum computation. In the quantum circuit model, a computation is modeled as a sequence of transformations on a data structure which is a quantum mechanical analog of an "n" bit register.