  We show that appropriate superpositions of motional states are a reference
frame resource that enables breaking of time -reversal superselection so that
two parties lacking knowledge about the other's direction of time can still
communicate. We identify the time-reversal reference frame resource states and
determine the corresponding frameness monotone, which connects time-reversal
frameness to entanglement. In contradistinction to other studies of reference
frame quantum resources, this is the first analysis that involves an
antiunitary rather than unitary representation.
