Bhattacharjee Abhinandan, Joshi Mritunjay K, Karan Suman, Leach Jonathan, Jha Anand K
Department of Physics, Indian Institute of Technology Kanpur, Kanpur UP 208016, India.
School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Sci Adv. 2022 Aug 5;8(31):eabn7876. doi: 10.1126/sciadv.abn7876.
Although the continuous-variable position-momentum entanglement of photon pairs produced by parametric down-conversion has applicability in several quantum information applications, it is not suitable for applications involving long-distance propagation. This is because entanglement in the position-momentum bases, as seen through Einstein-Podolsky-Rosen (EPR)-correlation measurements, decays very rapidly with photons propagating away from the source. In contrast, in this article, we show that in the continuous-variable bases of angle-orbital angular momentum (OAM), the entanglement, as seen through EPR-correlation measurements, exhibits a remarkably different behavior. As with the position-momentum bases, initially, the entanglement in the angle-OAM bases also decays with propagation, and after a few centimeters of propagation, there is no angle-OAM entanglement left. However, as the photons continue to travel further away from the source, the entanglement in the angle-OAM bases revives. We theoretically and experimentally demonstrate this behavior and show that angle-OAM entanglement revives even in the presence of strong turbulence.
