The growing recognition that entanglement is not exclusively a quantum property, and does not even originate with Schrödinger’s famous remark about it [Proc. Cambridge Philos. Soc. 31, 555 (1935)], prompts the examination of its role in marking the quantum-classical boundary. We have done this by subjecting correlations of classical optical fields to new Bell-analysis experiments and report here values of the Bell parameter greater than ℬ=2.54. This is many standard deviations outside the limit ℬ=2 established by the Clauser–Horne–Shimony–Holt Bell inequality [Phys. Rev. Lett. 23, 880 (1969)], in agreement with our theoretical classical prediction, and not far from the Tsirelson limit ℬ=2.828…. These results cast a new light on the standard quantum-classical boundary description, and suggest a reinterpretation of it.
X. F. Qian, B. Little, J. C. Howell, and J. H. Eberly, Shifting the Quantum-Classical Boundary: Theory and Experiment for Statistically Classical Optical Fields, Optica 2(7), 611-615. https://doi.org/10.1364/OPTICA.2.000611