Clauser-Horne/Eberhard inequality violation by a local model

TL;DR

This paper presents a local model that can violate the Clauser-Horne/Eberhard inequality by exploiting the source emission rate, challenging assumptions about the detection loophole and impacting quantum nonlocality tests.

Contribution

It introduces a local model that violates the inequality through a plausible mechanism involving the source emission rate, with implications for experimental design and interpretation.

Findings

A local model can violate the inequality using emission rate parameters.

The coincidence counting method accurately detects true coincidences.

Experimental data can be explained by local models if emission rates are not properly limited.

Abstract

Thanks to its immunity to the detection loophole, the Clauser-Horne/Eberhard inequality plays an important role in tests of locality and in certification of quantum information protocols based on entanglement. I describe a local model that violates the inequality using a plausible mechanism relying upon a parameter of the apparatus, the source emission rate. The effect is generated through the analysis of time-tagged data using a standard windowed coincidence counting method. Significantly, the detection times here are not functions of the measurement settings, i.e., the fair coincidences assumption is satisfied. This finding has implications for the design and interpretation of experiments and for quantum information protocols, as it shows that the coincidence window mechanism cannot be eliminated by a demonstration of independence of the detection times and settings. The paper describes a reliable coincidence counting method and shows that it delivers an accurate count of true coincidences. Recent experimental tests of local realism based on the Clauser-Horne/Eberhard inequality are considered and it is shown that in one case (Christensen et al.) the emission rate is appropriately limited to ensure valid counting, and the data supports locality; in a second case (Giustina et al.) the experiment neglects to appropriately limit the emission rate, and the claimed violation can be accounted for locally.