Probing quantum causality with geometric asymmetry in spatial-temporal correlations  

作　　者：Yu MENG Zheng-Hao LIU Zhikuan ZHAO Peng YIN Yi-Tao WANG Wei LIU Zhi-Peng LI Yuan-Ze YANG Zhao-An WANG Jin-Shi XU Shang YU Jian-Shun TANG Chuan-Feng LI Guang-Can GUO 

机构地区：[1]CAS Key Laboratory of Quantum Information,University of Science and Technology of China,Hefei 230026,China [2]CAS Center for Excellence in Quantum Information and Quantum Physics,University of Science and Technology of China,Hefei 230026,China [3]Department of Computer Science,Eidgenossische Technische Hochschule Zurich,Zurich 8092,Switzerland [4]Department of Physics,Imperial College London,London SW72AZ,UK [5]Research Center for Quantum Sensing,Zhejiang Lab,Hangzhou 310000,China [6]Hefei National Laboratory,Hefei 230088,China

出　　处：《Science China(Information Sciences)》2024年第9期290-301,共12页中国科学（信息科学）（英文版）

基　　金：supported by Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301200);National Natural Science Foundation of China(Grant Nos.12174370,12174376,11821404,11904356);Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017492);Open Research Projects of Zhejiang Lab(Grant No.2021MB0AB02);Fok Ying-Tong Education Foundation(Grant No.171007);Engineering and Physical Sciences Research Council and Quantum Computing and Simulation Hub(Grant No.T001062);Fundamental Research Funds for the Central Universities(Grant No.WK2030000008)。

摘　　要：Causation promotes the understanding of correlation to an advanced stage by elucidating its underlying mechanism.Although statisticians have specified the possible causal relations among correlations,inferring causal structures is impossible from only the observed correlations in the classical world.Quantum correlations encapsulating the most defining aspects of quantum physics have taken a new turn for the causal inference problem—the two-point spatial and temporal quantum correlations with observationally discernible characteristics correspond exactly to the two most basic causal structures.However,a direct causal interpretation for quantum correlations has only been established in very limited cases.Here,we explore to what extent quantum correlations promote causal inference.Theoretically,we have found that the distinguishable causal regime of two-point Pauli correlations can be expanded from a single value to an asymmetric interval,and the causal structures determining the quantum correlations can be interpreted by a simple distance criterion.Experimentally,we have devised and implemented a versatile non-unital quantum channel in an optical architecture to directly observe such an asymmetric interval.The setup enabled quantum causal inference without any requirement of active intervention,which is impossible in the classical realm.Our work facilitates the identification of causal links among quantum variables and provides insight into characterizing causation and spatial-temporal correlation in quantum mechanics.

关 键 词：CAUSALITY quantum information quantum channel channel-state duality non-unital channel 

分 类 号：O413[理学—理论物理]