A double-slit 'which-way' experiment on the complementarity–uncertainty debate

R Mir, J S Lundeen, M W Mitchell, A M Steinberg, J L Garretson, H M Wiseman
2007 New Journal of Physics  
A which-way measurement in Young's double-slit will destroy the interference pattern. Bohr claimed this complementarity between wave- and particle behaviour is enforced by Heisenberg's uncertainty principle: distinguishing two positions a distance s apart transfers a random momentum q \sim \hbar/s to the particle. This claim has been subject to debate: Scully et al. asserted that in some situations interference can be destroyed with no momentum transfer, while Storey et al. asserted that Bohr's
more » ... sserted that Bohr's stance is always valid. We address this issue using the experimental technique of weak measurement. We measure a distribution for q that spreads well beyond [-\hbar/s, \hbar/s], but nevertheless has a variance consistent with zero. This weakvalued momentum-transfer distribution P_{wv}(q) thus reflects both sides of the debate.
doi:10.1088/1367-2630/9/8/287 fatcat:nrufj46wonb3lnziuntjnja2xm