  State-average calculations based on mixture of states are increasingly being
exploited across chemistry and physics as versatile procedures for addressing
excitations of quantum many-body systems. If not too many states should need to
be addressed, calculations performed on individual states is also a common
option. Here we show how the two approaches can be merged into one method,
dealing with a generalized yet single pure state. Implications in electronic
structure calculations are discussed and for quantum computations are pointed
out.
