Ursin Group
ÖAW   Quantum Physics and Quantum Communication
Quantum Physics and Quantum Communication - Ursin Group
Quantum Physics and Quantum Communication – Ursin Group

Quantum erasure with causally disconnected choice

Author(s): J. Kofler, A. Qarry, N. Tetik, T. Scheidl, R. Ursin, S. Ramelow, T. Herbst, L. Ratschbacher, A. Fedrizzi, T. Jennewein, A. Zeilinger

Journal: PNAS

Volume: 110

Page(s): 1221-1226

Year: 2013

DOI Number: 10.1073/pnas.1213201110

Link: Link to publication


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.

Note: http://arxiv.org/abs/1206.6578

Zeilinger Group Zeilinger Group , Ursin Group