Locality and nonlocality in the interaction-free measurement
Department of Physics, Ben-Gurion University of the Negev, Beersheba 84105 Israel
2 School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
3 Department of Physics, Chapman University, Orange CA, USA
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Published online: 3 August 2018
We present a paradox involving a particle and a mirror. They exchange a nonlocal quantity, modular angular momentum Lz mod 2ћ, but there seems to be no local interaction between them that allows such an exchange. We demonstrate that the particle and mirror do interact locally via a weak local current 〈Lz mod 2ћ〉w. In this sense, we transform the “interaction-free measurement” of Elitzur and Vaidman, in which two local quantities (the positions of a photon and a bomb in the two arms of a Mach-Zehnder interferometer) interact nonlocally, into a thought experiment in which two nonlocal quantities (the weak modular angular momentum of the particle and of the mirror) interact locally.
© The Authors, published by EDP Sciences 2018
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