CRG-B thermal neutron interferometer S18

Quantum contextuality

In 2009, the polarised interferometer option of S18 has revealed new secrets of quantum mechanics. It demonstrates that quantum mechanics is generally in contradiction with non-contextuality, whatever the quantum state of the system.

Triple entangled states (spin, beam path, energy) can be produced and analysed. It has been used to demonstrate quantum contextuality for the first time.

Bell-like inequalities have been proven. Bell-theorem is a special case of a broader phenomenon called the Kochen-Specker theorem. An experimental test of the latter has been performed and the violation of non-contextual hidden-variable was observed.

This results may have significant consequences, like on possible new forms of quantum cryptography and more generally on all quantum-information-processing technologies.