Experimental determination of tripartite quantum discord

• 成果类型: Article
• 署名作者: Gulati, Vaishali; Bhowmick, Shaileyee; Byrnes, Tim; Radhakrishnan, Chandrashekar; Dorai, Kavita
• 署名单位: Indian Institute of Science Education & Research (IISER) - Mohali; New York University; NYU Shanghai; East China Normal University; New York University; New York University; NYU Shanghai
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13794
• DOI: 10.1073/pnas.2507467122
• 发表日期: 2025-07-08
• 关键词: entanglement; implementation; state

摘要

Quantum discord is a measure of nonclassical correlations in quantum systems. While the bipartite version of quantum discord is experimentally well-studied, the multipartite version has never been convincingly measured. In this study, we experimentally investigate tripartite quantum discord using an NMR quantum information processor. Building on a theoretical framework for conditional projective measurements and quantum conditional mutual information, we quantify the tripartite quantum discord and its contributions in different three-qubit states such as the Greenberger-Horne-Zeilinger (GHZ) and Werner (W) states as well as classical mixtures of biseparable Bell states, and classical mixtures of product states. The experiments employed full quantum state tomography and temporal averaging to prepare mixed states, achieving fidelities exceeding 95%. Our results confirm that quantum discord persists even in the absence of entanglement, highlighting its utility as a broader indicator of quantum correlations. Furthermore, we validate the nonconvexity of discord, confirming that classical mixtures of zero-discord states can exhibit nonzero discord. This experimentally confirms that quantum discord does not fit into the framework of resource theory. This work establishes a robust methodology for measuring quantum discord, illuminating the structure and distribution of quantum correlations in multipartite systems.