  We propose scalable architectures for the coherence-preserving qubits
introduced by Bacon, Brown, and Whaley [Phys. Rev. Lett. {\bf 87}, 247902
(2001)]. These architectures employ extra qubits providing additional degrees
of freedom to the system. We show that these extra degrees of freedom can be
used to counter errors in coupling strength within the coherence-preserving
qubit and to combat interactions with environmental qubits. The presented
architectures incorporate experimentally viable methods for inter-logical-qubit
coupling and can implement a controlled phase gate via three simultaneous
Heisenberg exchange operations. The extra qubits also provide flexibility in
the arrangement of the physical qubits. Specifically, all physical qubits of a
coherent-preserving qubit lattice can be placed in two spatial dimensions. Such
an arrangement allows for universal cluster state computation.
