  Quantum computers, much like their classical counterparts, will likely
benefit from flexible qubit encodings that can be matched to different tasks.
For trapped ion quantum processors, a common way to access multiple encodings
is to use multiple, co-trapped atomic species. Here, we outline an alternative
approach that allows flexible encoding capabilities in single-species systems
through the use of long-lived metastable states as an effective, programmable
second species. We describe the set of additional trapped ion primitives needed
to enable this protocol and show that they are compatible with large-scale
systems that are already in operation.
