[OCQT Seminar] The quantum communication power of indefinite causal order

OIST Centre for Quantum Technologies (OCQT) Seminar

The OIST Center for Quantum Technologies (OCQT) is pleased to invite you to the next installment of the OCQT Seminar Series. This time, we are excited to host Prof. Giulio Chiribella from the University of Hong Kong, who will deliver a talk entitled:

“The quantum communication power of indefinite causal order”

Date and time

Friday, December 5, 2025 – 10:30 - 12:00

Location

Seminar Room B503 – Center Building

Abstract

Quantum theory is in principle compatible with scenarios where physical processes occur in an indefinite causal order, potentially yielding advantages in various information processing tasks.
However, advantages in communication, the most basic form of information processing, have so far remained controversial and hard to prove. In this talk, I will provide a general framework for assessing the role of causal order in  communication, providing a rigorous way to compare operations with different causal structures. Using this framework, I will show a clear-cut  advantage of indefinite causal order in classical communication, and, at the same time, I will present some fundamental limits to the  communication power of quantum operations with indefinite causal order.  Notably, a special form of indefinite causal order, obtained by coherently controlling the order of two processes, can enhance the transmission of classical messages in a one-shot scenario, but no quantum operation with  indefinite order can offer advantages over shared entanglement when asymptotically many uses of the same communication device are employed.

Biography

Professor Giulio Chiribella is the founding director of QICI Quantum Information and Computation Initiative, and Associate Director (Research and Graduate Programs) of the School of Computing and Data Science of The University of Hong Kong. He has done pioneering research on quantum causality, on the information-theoretic foundations of quantum theory, and on the ultimate precision limits of quantum measurements, for which he was awarded the Hermann Weyl Prize 2010. In 2020 and 2018 he received Senior Research Fellowships from the Hong Kong Research Grant Council (RGC) and from the Croucher Foundation, respectively. He currently serves as an elected member of the Hong Kong Young Academy of Sciences, a Young Member of the Hong Kong Academy of Engineering Sciences, a visiting professor at the University of Oxford, and as an Editorial Board Member of the journals Communications in Mathematical Physics and Physical Review X Quantum. Before joining the University of Hong Kong, he held faculty positions at Oxford University and Tsinghua University, Beijing.