Excepting event-ready setups, Bell experiments require post-selection of data to define coincidences. From the fundamental point of view, post-selection is a true 'logical loophole'. From the practical point of view, it implies a numerically heavy and time consuming task. In Quantum Key Distribution (QKD), it opens vulnerability in case of a hostile adversary. The core of the problem is to synchronize independent clocks during long observation runs. A pulsed source gets rid of clocks' drift, but there is still the problem of identifying the same pulse in each remote station. We use a frequency modulated pulsed source to achieve it. This immediately defines the condition of valid coincidences in a manner that is unaffected by the drift between the clocks. It allows finding the set of entangled pairs avoiding post-selection and in a way that is found to be optimal. It is also robust against a hostile adversary in the case of QKD.
@article{arxiv.2307.03203,
title = {'Frequency-modulated' pulsed Bell setup avoids post-selection},
author = {Mónica Agüero and Alejandro Hnilo and Marcelo Kovalsky and Myriam Nonaka},
journal= {arXiv preprint arXiv:2307.03203},
year = {2023}
}