Quantum Operations In An Information Theory For Fermions

A reasonable quantum information theory for fermions must respect the parity superselection rule to comply with the special theory of relativity and the no-signaling principle. This rule restricts the possibility of any quantum state to have a superposition between even- and odd-parity fermionic states. thereby characterizing the set of physically allowed fermionic quantum states. Here we introduce the physically allowed quantum operations, in congruence with the parity superselection rule, that map the set of allowed fermionic states onto itself. We first introduce unitary and projective measurement operations of the fermionic states. We further extend the formalism to general quantum operations in the forms of Stinespring dilation, operator-sum representation, and axiomatic completely positive and trace-preserving maps. We explicitly show the equivalence between these three representations of fermionic quantum operations. We discuss the possible implications of our results in characterization of correlations in fermionic systems.