Symmetry protection of photonic entanglement in the interaction with a single nanoaperture

Open Access

Abstract

In this work, we experimentally show that quantum entanglement can be symmetry protected in the interaction with a single subwavelength plasmonic nanoaperture, with a total volume of V∼0.2λ3. In particular, we experimentally demonstrate that two-photon entanglement can be either completely preserved or completely lost after the interaction with the nanoaperture, solely depending on the relative phase between the quantum states. We achieve this effect by using specially engineered two-photon states to match the properties of the nanoaperture. In this way we can access a symmetry protected state, i.e., a state constrained by the geometry of the interaction to retain its entanglement. In spite of the small volume of interaction, we show that the symmetry protected entangled state retains its main properties. This connection between nanophotonics and quantum optics probes the fundamental limits of the phenomenon of quantum interference. ; L. M. and F. S. acknowledge financial support from the European Union Horizon 2020 program, within the European Research Council (ERC) Grant No. 694683, PHOSPhOR. G. M. T. acknowledges financial support from the Australian Research Council through the Future fellowship program FT110100924 and the Spanish Ministry of Science, Innovation and Universities (MICIN) Project No. FIS2017-87363-P. ; Peer reviewed