Characterizing the multipartite continuous-variable entanglement structure from squeezing coefficients and the Fisher information

Year: 2019

Authors: Qin ZZ., Gessner M., Ren ZH., Deng XW., Han DM., Li WD., Su XL., Smerzi A., Peng KC.

Autors Affiliation: Shanxi Univ, Inst Optoelect, State Key Lab Quantum Opt & Quantum Opt Devices, Taiyuan 030006, Shanxi, Peoples R China; Shanxi Univ, Collaborat Innovat Ctr Extreme Opt, Taiyuan 030006, Shanxi, Peoples R China; INO CNR, QSTAR, Largo Enrico Fermi 2, I-50125 Florence, Italy; LENS, Largo Enrico Fermi 2, I-50125 Florence, Italy; Shanxi Univ, Inst Theoret Phys, Taiyuan 030006, Shanxi, Peoples R China; Shanxi Univ, Dept Phys, Taiyuan 030006, Shanxi, Peoples R China; Shanxi Univ, Inst Laser Spect, Taiyuan 030006, Shanxi, Peoples R China.

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.

Journal/Review: NPJ QUANTUM INFORMATION

Volume: 5 (1)      Pages from: 3-1  to: 3-6

More Information: This research was supported by the National Natural Science Foundation of China (Grant Nos. 11522433, 11834010, 61601270, 61475092, and 11874247), National Key R&D Program of China (Grant Nos. 2016YFA0301402, 2017YFA0304500, and 2017YFA0304203), 111 project (Grant No. D18001), the Hundred Talent Program of the Shanxi Province (2018), Fund for Shanxi “1331” Project Key Subjects Construction, and the European Commission through the Quant-ERA project “CEBBEC”. X.S. thanks the program of Youth Sanjin Scholar. M.G. thanks the Alexander von Humboldt foundation for support. W.L. thanks PCSIRT (Grant No. IRT_17R70), and the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices (No. KF201703).
KeyWords: QUANTUM-NOISE; CRITERION; BEAMS
DOI: 10.1038/s41534-018-0119-6

Citations: 27
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