Physical meaning of the radial index of Laguerre-Gauss beams
William N. Plick,
Mario Krenn
Physical Review A
92
(6)
063841
(2015)
| Journal
| PDF
The Laguerre-Gauss modes are a class of fundamental and well-studied optical fields. These stable shape-invariant photons, exhibiting circular-cylindrical symmetry, are familiar from laser optics, micromechanical manipulation, quantum optics, communication, and foundational studies in both classical optics and quantum physics. They are characterized, chiefly, by two mode numbers: the azimuthal index indicating the orbital angular momentum of the beam, which itself has spawned a burgeoning and vibrant subfield, and the radial index, which up until recently has largely been ignored. In this paper we develop a differential operator formalism for dealing with the radial modes in both the position and momentum representations and, more importantly, give the meaning of this quantum number in terms of a well-defined physical parameter: the intrinsic hyperbolic momentum charge.
Twisted photon entanglement through turbulent air across Vienna
Mario Krenn,
Johannes Handsteiner,
Matthias Fink,
Robert Fickler,
Anton Zeilinger
Proceedings of the National Academy of Sciences of the United States of America
112
(46)
14197-14201
(2015)
| Journal
Photons with a twisted phase front can carry a discrete, in principle, unbounded amount of orbital angular momentum (OAM). The large state space allows for complex types of entanglement, interesting both for quantum communication and for fundamental tests of quantum theory. However, the distribution of such entangled states over large distances was thought to be infeasible due to influence of atmospheric turbulence, indicating a serious limitation on their usefulness. Here we show that it is possible to distribute quantum entanglement encoded in OAM over a turbulent intracity link of 3 km. We confirm quantum entanglement of the first two higher-order levels (with OAM=+/- 1h and +/- 2h). They correspond to four additional quantum channels orthogonal to all that have been used in long-distance quantum experiments so far. Therefore, a promising application would be quantum communication with a large alphabet. We also demonstrate that our link allows access to up to 11 quantum channels of OAM. The restrictive factors toward higher numbers are technical limitations that can be circumvented with readily available technologies.
Kontakt
Junior Forschungsgruppe Mario Krenn
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen
