  The entanglement between two bosons or fermions can be accessed if there
exists an auxiliary degree of freedom which can be used to label and
effectively distinguish the two particles. For some types of entanglement
between two indistinguishable particles one can observe duality, i.e., if the
entanglement is present in the Hilbert space H and an auxiliary Hilbert space
H' is used to label the particles, then if we used H as a label the
entanglement would be present in H'. For distinguishable particles this effect
does not occur because of superselection rules which prevent superpositions of
different types of particles. However, it is known that superselection rules
can be bypassed if one uses special auxiliary states that are known as
reference frames. Here we study properties of reference frames which allow for
an observation of a duality in entanglement between two distinguishable
particles. Finally, we discuss the consequences of this result from the
resource-theoretic point of view.
