Directly observing momentum transfer in twin-slit "which-way" experiments
نویسنده
چکیده
Making a position measurement to determine through which slit a particle has passed necessarily destroys the twin-slit interference pattern (see Fig. 1). This is the canonical example of Bohr’s complementarity principle [1, 2]. To defend this principle against Einstein’s recoiling slit gedankenexperiment, Bohr relied upon the recently (in 1927) derived Heisenberg uncertainty relation [3] to show that the position measurement would cause an “uncontrollable change in the momentum” ℘ & ~/s, where s is the slit separation [1]. This is just what is required to wash out the interference pattern, thereby enforcing complementarity. Bohr’s argument was famously reiterated by Feynman [4], for a measurement using Heisenberg’s light microscope [3].
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