SeMIOpT SASPRO2 1372/03/01

Title: Sequential measurements and incompatibility in operational theories
Duration: 01/09/2022 - 31/08/2025
Principal Investigator: Dr. Leevi Leppäjärvi
Mentor: Mário Ziman
Budget: 174 096 eur

Project Goals: The framework of operational theories provides an abstract setting for possible physical theories based on operational principles. Containing not only quantum and classical theories but also countless toy theories, the operational theories give us means to study well-known properties of quantum theory in a more general setting. This allows us to formulate and examine these properties in different theories, quantify them and compare different theories to each other based on how these properties behave within them. An important platform for comparing quantum theory to other operational theories are the prepare-and-measure scenarios. The prepare-and-measure scenarios consist of preparing a physical system in a desired state, measuring the system with some physical observable and finally registering the obtained measurement outcome. As a basis of every physical experiment and communication scheme it serves as the framework in which all information-theoretic tasks can be implemented. Studying these scenarios using the methods of operational theories helps us understand which type of communication is possible in quantum theory, what are the origins of the limitations for the different information-theoretic tasks and even what kind of theories could overcome the limits of quantum theory. An example of an important and well-studied property of quantum theory is the incompatibility of measurements, i.e., the impossibility to measure some physical observables jointly and sharply with a single joint measurement device. Incompatibility has many foundational and practical consequences. It has been shown that incompatibility is not only a property of quantum theory but also all other operational theories which are not classical; hence, incompatibility is a strongly non-classical feature, which can be efficiently studied in the framework of operational theories.

Researchers: Leevi Leppäjärvi