Testing Quantum Processes

The recent development of quantum communication protocols calls for adequate modelling and verification techniques, which requires abstracting and focusing on the basic features of quantum concurrent systems. Several quantum process calculi and behavioural equivalences have been proposed to address this problem, but they are often incompatible with the prescriptions of quantum theory, as they implicitly define omniscient observers that are capable of exactly discriminating the state of a physical system, therefore contradicting the uncertainty principle. In this paper, we directly model these observational limitations by resorting to testing equivalence for a quantum-capable version of CCS, building on the concrete actions and experiments that a real tester can perform. Thus, we obtain an equivalence notion pairing processes that cannot be distinguished by any physically implementable observer.