🤖 AI Summary
This work proposes a categorical framework applicable to arbitrary circuit theories to resolve the long-standing ambiguity in the definition of higher-order supermaps within generalized physical theories. By leveraging channel–state duality, the framework constructs explicit representations of supermaps and introduces a generalized Yoneda lemma to eliminate definitional ambiguities. This approach not only provides a rigorous foundation for higher-order processes in real quantum theory but also successfully incorporates higher-order operations from non-standard theories—such as Boxworld—into a unified formalism. Consequently, it establishes a universal and unambiguous definition of higher-order operations within the broader context of generalized probabilistic theories.
📝 Abstract
Categorical supermaps generalise higher-order quantum operations from finite-dimensional quantum theory to arbitrary circuit theories. In this paper, we establish the Yoneda lemma for categorical supermaps, which states that whenever a physical theory has a suitable notion of channel-state duality, then categorical supermaps on that theory can be concretely represented in terms of that duality. This lemma eliminates any guesswork or ambiguity when defining the appropriate notion of supermap for these theories. As a concrete application, we show that the recently proposed higher-order processes on boxworld can be obtained as a particular instance of categorical supermaps, and put forward a stable definition of higher-order real quantum theory.