2018/04/30 by Zhongzhong Qin, Manuel Gessner, Zhihong Ren +6 · 1 citation
Computer Science · Physics and Astronomy · #Entanglement witness #Fisher information #Multipartite entanglement #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum discord #Quantum entanglement #Quantum information #Quantum metrology #Quantum sensor #Quantum technology #Squashed entanglement #quant-ph
paper · pdf · doi:10.1038/s41534-018-0119-6
published as npj Quantum Information 5, 3 (2019)
openalex publication_date 2018/12/28 · openalex created_date 2019/01/25 · arxiv created 2019/01/29 · arxiv updated 2019/01/30 · openalex updated_date 2026/08/05
Abstract Understanding the distribution of quantum entanglement over many parties is a fundamental challenge of quantum physics and is of practical relevance for several applications in the field of quantum information. The Fisher information is widely used in quantum metrology since it is related to the quantum gain in metrology measurements. Here, we use methods from quantum metrology to microscopically characterize the entanglement structure of multimode continuous-variable states in all possible multi-partitions and in all reduced distributions. From experimentally measured covariance matrices of Gaussian states with 2, 3, and 4 photonic modes with controllable losses, we extract the metrological sensitivity as well as an upper separability bound for each partition. An entanglement witness is constructed by comparing the two quantities. Our analysis demonstrates the usefulness of these methods for continuous-variable systems and provides a detailed geometric understanding of the robustness of cluster-state entanglement under photon losses.