Mainz 2017 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 9: Quantum Communication II

Q 9.6: Talk

Monday, March 6, 2017, 18:15–18:30, P 3

Universal entanglement decay of twisted photons in a weakly turbulent atmosphere — •David Bachmann, Vyacheslav Shatokhin, and Andreas Buchleitner — Physikalisches Institut, Albert-Ludwigs-Universität, Freiburg i. Br., Germany

The propagation of entangled twisted photons that carry orbital angular momentum (OAM) through turbulent atmosphere has become a rapidly developing research area. This topic is motivated by the potential uses of the underlying unbounded Hilbert space associated with the OAM for quantum communication. However, atmospheric turbulence introduces random phase shifts to the photons’ phase profile, which is used for encoding quantum information, and eventually results in a loss of entanglement. Recently, it has been shown [1] that the entanglement decay of OAM qubit states in a weakly turbulent atmosphere is a universal function of a single parameter – the ratio between the OAM beam’s phase correlation length and the turbulence correlation length, but the explicit form of the decay law was not yet obtained.

In this talk, we present analytical expressions for the universal entanglement decay law of a biphoton state in weak atmospheric turbulence. These results are obtained for different models of the turbulence phase structure function, using asymptotic methods. Thereby, we establish the explicit relationship between the turbulence-induced coupling strength between different OAM modes and the specific form of the decay law.

[1] N. D. Leonhard et al., Phys. Rev. A 91, 012345 (2015).