Quantum erasure with causally disconnected choice
Abstract
The counterintuitive features of quantum physics challenge many common-sense assumptions. In an interferometric quantum eraser experiment, one can actively choose whether or not to erase which-path information, a particle feature, of one quantum system and thus observe its wave feature via interference or not by performing a suitable measurement on a distant quantum system entangled with it. In all experiments performed to date, this choice took place either in the past or, in some delayed-choice arrangements, in the future of the interference. Thus in principle, physical communications between choice and interference were not excluded. Here we report a quantum eraser experiment, in which by enforcing Einstein locality no such communication is possible. This is achieved by independent active choices, which are space-like separated from the interference. Our setup employs hybrid path-polarization entangled photon pairs which are distributed over an optical fiber link of 55 m in one experiment, or over a free-space link of 144 km in another. No naive realistic picture is compatible with our results because whether a quantum could be seen as showing particle- or wave-like behavior would depend on a causally disconnected choice. It is therefore suggestive to abandon such pictures altogether.
Cite
@article{arxiv.1206.6578,
title = {Quantum erasure with causally disconnected choice},
author = {Xiao-song Ma and Johannes Kofler and Angie Qarry and Nuray Tetik and Thomas Scheidl and Rupert Ursin and Sven Ramelow and Thomas Herbst and Lothar Ratschbacher and Alessandro Fedrizzi and Thomas Jennewein and Anton Zeilinger},
journal= {arXiv preprint arXiv:1206.6578},
year = {2013}
}