  Quantum information stored in a qubit is rapidly lost to the environment. The
realization of robust qubits is one of the most important challenges in quantum
computing. Herein we propose to embed a logical qubit within the manifold of a
qudit as a scheme to preserve quantum information over extended periods of
time. Under identical conditions (e.g. decoherence channels) the submanifold of
the logical qubit exhibits extended lifetimes compared to a pure two-level
system (qubit). The retention of quantum information further improves with
separation between the sublevels of the logical qubit. Lifetime enhancement can
be understood in terms of entropy production of the encoding and non-encoding
subspaces during evolution under a quantum map for a $d$-level system. The
additional pathways for coherent evolution through intermediate sublevels
within a $d$-level manifold provide an information-preserving mechanism:
reversible alternative channels to the irreversible loss of information to the
environment characteristic of open quantum systems.
