报告人：肖运龙
报告时间：2025年12月4日下午15:00-16:00
报告地点：国交2号楼201会议室
报告摘要：Quantum information cannot be broadcast — an intrinsic limitation imposed by quantum mechanics. However, recent advances in virtual operations offer new insights into the no-broadcasting theorem. Here, we focus on the practical utility and introduce sample efficiency as a fundamental constraint, requiring any practical broadcasting protocol perform no worse than the naive approach of direct preparation and distribution. We prove that no linear process — whether quantum or beyond — can simultaneously uphold sample efficiency, unitary covariance, permutation invariance, and classical consistency. This leads to a no-practical-broadcasting theorem, which places strict limits on the practical distribution of quantum information. By applying Schur-Weyl duality, we establish the uniqueness of the canonical 1-to-N virtual broadcasting map that satisfies the latter three conditions, provide its construction, and determine its sample complexity through semidefinite programming. Finally, we explore the interplay between virtual broadcasting and a quantum spacetime framework, known as the pseudo-density operator, showing that their correspondence holds only in the 1-to-2 case, underscoring the fundamental asymmetry between spatial and temporal statistics in the quantum world.
报告人简介：Yunlong Xiao earned his Ph.D. in Mathematical Physics from the Max Planck Institute for Mathematics in the Sciences (MiS) in Leipzig, Germany, and a second Ph.D. in Pure Mathematics from South China University of Technology. He subsequently held a Postdoctoral Fellowship at the Institute for Quantum Science and Technology at the University of Calgary until August 2019, followed by a Research Fellowship at the Quantum Hub in the School of Physical and Mathematical Sciences at Nanyang Technological University, Singapore. He is now a Senior Scientist at the Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), Singapore. His research spans quantum foundations, quantum causal inference, quantum resource theory, and quantum communication, with publications in Physical Review Letters, Physical Review Research, Physical Review D, Light: Science & Applications, npj Quantum Information, Communications Physics, Quantum Science and Technology, and New Journal of Physics. His broader impact includes long talks and contributed talks at major international venues such as APS March Meeting, AQIS, QPL, and QIP.
