Frequency-modulated pulsed Bell setup avoids post-selection

Abstract

Bell experiments require post-selection of data to define coincident detections. In the case of stations of observation placed far away from each other, this implies a heavy and time consuming numerical task of convolution of time series, and may lead to poor results. 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 test using a “frequency modulated” pulsed source to achieve it. This method is found to immediately and optimally define the set of entangled pairs. Besides, it is robust against a hostile adversary in comparison with GPS-synchronization. The tested method is of interest in both pure and applied experiments with entangled states observed in remote stations.