Nature 275, 188 - 191 (21 September 1978); doi:10.1038/275188a0

Young's double beam interference experiment with spinor and vector waves

J. Byrne

School of Mathematical and Physical Sciences, University of Sussex, Brighton, Sussex, UK

The fringe shift observed in Young's double beam interference experiment using unpolarised neutrons, when one beam traverses a magnetic field before recombination, has been interpreted as implying direct observation of the sign reversal of a spinor wave function subjected to a 2 rotation. This interpretation is unsatisfactory because for any fermion the relative rotation of the spins in the two beams and the interference pattern are mutually incompatible observables. This incompatibility does not arise in the case of bosons which possess a state of zero spin-component. Furthermore, equivalent 'sign-reversal' effects may be observed in interference phenomena associated with any two-state system and a realisable photon analogue is proposed.

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