With the data from above definition we can now define also the category of quantum automata as
follows.
Definition 0.2. The category of quantum automata 𝒬A is defined as an algebraic category
whose objects are triples (,Δ : →,μ) (where is either a Hilbert space or a rigged Hilbert space
of quantum states and operators acting on , and μ is a measure related to the quantum logic,
LM, and (quantum) transition probabilities of this quantum system), and whose morphisms
are defined between such triples by homomorphisms of Hilbert spaces, Ø : →, naturally
compatible with the operators Δ, and by homomorphisms between the associated Haar
measure systems.
An alternative definition is also possible based on Quantum Algebraic Topology.
Definition 0.3. A quantum algebraic topology definition of the category of quantum
algebraic automata involves the objects specified above in Definition 0.1 as quantum
automaton triples (QA), and quantum automata homomorphisms defined between such
triples; these QA morphisms are defined by groupoid homomorphisms h : 𝒢 → 𝒢∗ and
α : Aut(𝒢) → Aut(𝒢∗), together with unitarity preserving mappings u between unitary
representations of 𝒢 on rigged Hilbert spaces (or Hilbert space bundles).