Speaker: Masahito Hayashi (The Chinese University of Hong Kong, Shenzhen/Nagoya University)

Title: Indefinite causal order strategy nor adaptive strategy does not improve the estimation of group action

Time/Date: 4:45-6:15pm, April 8 (Tue), 2025

Room: 126 Math Sci Building (It will be also online. The Zoom link is the same as before. If you don't have one, please ask Kawahigashi.)

Abstract: We consider estimation of unknown unitary operation when the set of possible unitary operations is given by a projective unitary representation of a compact group. We show that indefinite causal order strategy nor adaptive strategy does not improve the performance of this estimation when error function satisfies group covariance. That is, the optimal parallel strategy gives the optimal performance even under indefinite causal order strategy and adaptive strategy. This result is a generalization of the following result.

M. Hayashi, "Fourier Analytic Approach to Quantum Estimation of Group Action," Communications in Mathematical Physics, Volume 347, Number 1, 3-82 (2016).

The result is available from https://arxiv.org/abs/2501.09312.