Controlling neutron orbital angular momentum

• Autores: Charles W. Clark, Roman Barankov, Michael G. Huber, Muhammad Arif, David G. Cory, Dmitry A. Pushin
• Localización: Nature: International weekly journal of science, ISSN 0028-0836, Vol. 525, Nº 7570, 2015, págs. 504-506
• Idioma: inglés
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• Resumen

  • The quantized orbital angular momentum (OAM) of photons1 offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications2,3 ranging from studies of quantum entanglement and quantum information science4,5,6,7 to imaging8,9,10,11,12. The OAM states of electron beams13,14,15 have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals16,17,18,19. However, although neutrons—as massive, penetrating and neutral particles—are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a ‘twist’ to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science20,21, the foundations of quantum mechanics22,23, and scattering and imaging24 of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies.