Freiburg 2019 – wissenschaftliches Programm
FM 52.4: Talk
Mittwoch, 25. September 2019, 15:00–15:15, 1009
High-dimensional entanglement in atmospheric turbulence — •Giacomo Sorelli1, Nina Leonhard2, Claudia Reinlein2, Vyacheslav N. Shatokhin1, and Andreas Buchleitner1 — 1Physikalisches Institut, Albert-Ludwigs-Universität Freiburg i. Br. — 2Fraunhofer Institute for Applied Optics and Precision Engineering, Jena
Discrete high-dimensional quantum states (qudits) offer several advantages over their two dimensional counterpart (qubits). In particular, qudits increase the amount of information encoded into a single carrier. Moreover, in entanglement-based QKD the intervention of an eavesdropper is excluded by the violation of a Bell inequality, which is the more violated the larger the dimensionality of the employed states. Spanning a discrete infinite-dimensional Hilbert space, the orbital angular momentum (OAM) of light can be used to realize such high-dimensional quantum systems. However, its use in free-space QKD is severely limited by phase distortions introduced by random refractive index fluctuations due to atmospheric turbulence.
We discuss the efficiency of adaptive optics (AO) in mitigating turbulence-induced signal and entanglement losses of OAM states, for a vast range of atmospheric conditions. We show that the stronger Bell correlations available in higher dimensions are nullified by their faster turbulence-induced decay. In contrast, AO corrections allow to restore non-locality, and thus the security of entanglement-based quantum communication, even for high-dimensional states in moderate turbulence.