Shintaro Minagawa: Quantum channel incompatibility: A fundamental principle constraining quantum communication and quantum measurement

mardi 3 nov. 2026, 10:30 → 11:30 Europe/Paris

A quantum channel is a mathematical description of the evolution or processing of a quantum system. Sometimes, multiple quantum channels cannot be realized simultaneously as parts of a single joint channel; this phenomenon is known as quantum channel incompatibility [1]. Quantum channel incompatibility provides a unified perspective on various phenomena, such as the no-broadcasting theorem [2] in quantum communication and the unavoidable disturbance that occurs when extracting information through quantum measurements [3]. In this talk, moving beyond such qualitative no-go theorems, we address the question of the minimum total error incurred when attempting to jointly realize incompatible quantum channels. We show that the minimum total error is bounded from above and below in terms of the generalized robustness of incompatibility, a measure of channel incompatibility that can be computed via convex optimization. By applying this result to quantum measurements, we also derive a universal tradeoff between the informativeness of a quantum measurement, measurement error, and the resulting disturbance. This talk is based on our work [4]. 

[1] T. Heinosaari and T. Miyadera, J. Phys. A: Math. Theor. 50, 135302 (2017).
[2] H. Barnum, C. M. Caves, C. A. Fuchs, R. Jozsa, and B. Schumacher, Phys. Rev. Lett. 76, 2818 (1996).
[3] P. Busch, “No Information Without Disturbance”: Quantum Limitations of Measurement. In: Quantum Reality, Relativistic Causality, and Closing the Epistemic Circle. The Western Ontario Series in Philosophy of Science, vol 73. Springer, Dordrecht (2009).
[4] S. Minagawa, R. Takakura, and K. Torii, arXiv:2605.11924 (2026).