Two very similar proposals have been made recently for witnessing nonclassical features of gravity, by Bose et al. and by Marletto and Vedral. However, while these proposals are asserted to be very general, they are in fact based on a very strong claim: that quantum systems cannot become entangled via a classical intermediary. We point out that the support provided for this claim is only applicable to a very limited class of quantum-classical interaction models, corresponding to Koopman-type dynamics. We show that the claim is also valid for mean-field models, but that it is contradicted by explicit counterexamples based on the configuration-ensemble model. Thus, neither proposal provides a definitive test of nonclassical gravity.
Reassessing the boundary between classical and nonclassical for individual quantum processes
Institute for Quantum Computing, University of Waterloo（滑铁卢大学量子计算研究所）；Perimeter Institute for Theoretical Physics（理论物理前沿研究所）；Department of Physics & Astronomy, University of Waterloo（滑铁卢大学物理与天文学系）
Factorization of multimeters: a unified view on nonclassical quantum phenomena
Faculty of Information Technology, University of Jyväskylä（于韦斯屈莱大学信息技术学院）；Naturwissenschaftlich-Technische Fakultät, Universität Siegen（锡根大学自然科学与技术学院）；Univ. Grenoble Alpes, CNRS, Grenoble INP, LIG（格勒诺布尔阿尔卑斯大学、法国国家科学研究中心、格勒诺布尔理工学院、信息学与图像与信号实验室）；Laboratoire de Physique Théorique, Université de Toulouse, CNRS, UPS（图卢兹大学理论物理实验室、法国国家科学研究中心、图卢兹第三大学）；Institut für Theoretische Physik, Leibniz Universität Hannover（汉诺威莱布尼茨大学理论物理研究所）
Interaction of light and semiconductor can generate quantum states required for solid state quantum computing: Entangled, steered and other nonclassical states
Shiv Nadar Institution of Eminence（希夫纳德卓越机构）；ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology（ICFO-光子科学研究所，巴塞罗那科学技术研究院）；ETH Zürich（苏黎世联邦理工学院）；University College London（伦敦大学学院）
Gravity-mediated entanglement via infinite-dimensional systems
Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences（奥地利科学院量子光学与量子信息研究所）；Vienna Center for Quantum Science and Technology (VCQ), Faculty of Physics, University of Vienna（维也纳大学物理学院维也纳量子科学与技术中心）；Department of Science and Industry Systems, University of South-Eastern Norway（挪威东南大学科学与产业系统系）；Perimeter Institute for Theoretical Physics（理论物理前沿研究所）
Gaussian geometric discord, entanglement and EPR-steering of two rotational mirrors in a double Laguerre-Gaussian cavity optomechanics in the presence of YIG sphere
Evolution of tripartite entanglement in three-qubit Quantum Gravity-Induced Entanglement of Masses (QGEM) with quantum decoherence
Instituto de Física Teórica, UAM-CSIC（理论物理研究所，UAM-CSIC）；Van Swinderen Institute for Particle Physics and Gravity, University of Groningen（格罗宁根大学范斯温德恩粒子物理与引力研究所）；Departamento de Física Teórica and CIAFF, Universidad Autónoma de Madrid（马德里自治大学理论物理系及CIAFF）
