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Measurement of a confinement induced neutron phase


Particle physicists see neutrons as tiny massive particles with a confinement radius of about 0.7 fm and a distinct internal quark–gluon structure. In quantum mechanics, neutrons are described by wave packets whose spatial extent may become ten orders of magnitude larger than the confinement radius, and can even reach macroscopic dimensions, depending on the degree of monochromaticity. For neutrons passing through narrow slits, it has been predicted1,2 that quantization of the transverse momentum component changes the longitudinal momentum component, resulting in a phase shift that should be measurable using interferometric methods3. Here we use neutron interferometry to measure the phase shift arising from lateral confinement of a neutron beam passing through a narrow slit system. The phase shift arises mainly from neutrons whose classical trajectories do not touch the walls of the slits. In this respect, the non-locality of quantum physics is apparent.

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Figure 1: Sketch of the slit structure and of the related neutron–wall interaction potential.
Figure 2: Expected phase shift as a function of the angle α of the incident beam component.
Figure 3: Sketch of the experimental set-up.
Figure 4: Typical interference pattern with and without the phase-shifting slit system (a) and the collection of the results of various scans (b).


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This work was supported by the Austrian Science Foundation and a TMR-Network of the European Union EU. Useful discussions with J. Summhammer and D. Petrascheck are gratefully acknowledged.

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Correspondence to H. Rauch.

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Rauch, H., Lemmel, H., Baron, M. et al. Measurement of a confinement induced neutron phase. Nature 417, 630–632 (2002).

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