Refinement orders for quantum programs

Abstract: Refinement is an influential technique used in the verification and development of computer programs. It provides a systematic and rigorous approach to software development through stepwise refinement, where a high-level abstract specification is progressively transformed into an implementation that meets the desired requirements. Central to this technique is the notion of a refinement order, which ensures that each refinement step preserves program correctness. Different orders can be defined with respect to partial and total correctness, as well as for deterministic and nondeterministic programs. In the realm of quantum programs, the theory becomes even more intricate due to the existence of various quantum state predicates, leading to different notions of specifications. This paper thoroughly explores different refinement orders for quantum programs and examines the relationships between them.