Nonlinear Bell inequality for macroscopic measurements

The correspondence principle suggests that quantum systems grow classical when large. Classical cannot violate Bell inequalities. Yet agents given substantial control can inequalities proven for large-scale systems. We consider who have little control, implementing only general operations suited to macroscopic experimentalists: preparing small-scale entanglement and measuring properties while suffering from noise. That experimentalists so restricted a inequality appears unlikely, in light of earlier literature. we prove such an agent violate, even if experimental errors variances scale as the system size. A violation implies nonclassicality, limitations on particles' interactions. product singlets violates inequality; tests are feasible photons, solid-state systems, atoms, trapped ions. Consistently with known results, violations our disprove local hidden-variables theories. By rejecting disproof goal, show, one certify nonclassical correlations under reasonable assumptions.Received 8 December 2019Revised 13 July 2020Accepted 22 2020DOI:https://doi.org/10.1103/PhysRevA.103.L010202©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAtomic & molecular processes external fieldsMesoscopicsPhotonicsQuantum entanglementQuantum foundationsQuantum nonlocalityQuantum opticsQuantum protocolsAtomic, Molecular OpticalGeneral PhysicsQuantum Information