General ILL seminar
organised by College 3
Thursday October 23, 2025 at 10h30
Seminar room 110-111, ILL 50, 1st floor
Zoom link: https://ill.zoom.us/j/98964195699?pwd=vPhNT17CAeoDUr7QX4PjfyPnWsHuMU.1
Password: SeminarC3
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“Generation and Detection of Neutron Orbital Angular Momentum”
Niels Geerits
TU Wien Austria, niels.geerits@tuwien.ac.at
In matter wave optics orbital angular momentum (OAM) is a type of azimuthal structure imprinted on the wavefunction that contributes to the total angular momentum of the particle. In the simplest case this azimuthal structure is just a linearly varying azimuthal phase (i.e. e^ilϕ). We can easily see that for integer l these functions are orthogonal on 0<ϕ≤2π. In addition, it turns out integer l are sufficient to form a complete basis. The OAM degree of freedom is therefore quantized and able to describe any type of general azimuthal structure. Given that OAM is both quantized and capable of providing an infinite number of levels, it could be used to implement a qudit. A qudit is a generalization of the binary two level qubit to an arbitrary number of levels. Hence, it has been argued that OAM is of significant interest to the field of quantum information and contextuality.
Pure OAM states have been successfully demonstrated in various matter waves, such as electrons, neutrons and atoms. Neutrons face a host of practical challenges, arising from the small spatial coherence of cold and thermal beams and comparatively low flux. Therefore, creative techniques are required to produce and measure OAM in neutrons.
After a short introduction to OAM, its applications and short history of neutron OAM this talk will cover the most promising techniques for OAM generation, such as coherent averaging, the Schwinger effect and diffraction from forked gratings, in addition to detection techniques like self interference and OAM rotation coupling known as the quantum Sagnac effect.
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Hanno Filter (College 3 Secretary)
External visitors may ask for a site access to tellier(at)ill.fr