In instruction, most discussions about entanglement start with either the Einstein–Podolsky–Rosen experiment, or Bohm’s variant of it with spin. This introduces an extra issue related to signaling, causality, and “spooky action at a distance.” Often students focus primarily on these extraneous issues and miss the basic properties of entanglement, in particular the way a product-state superposition displays interference effects, but entangled superpositions do not. In this work, we discuss an alternative way to teach entanglement using a two-slit experiment with crossed polarizers at the slits that provide “which-way” information destroying interference and then illustrate how one can remove “which-way” information via a delayed-choice variant. This work complements recent experimental illustrations of these setups using single-photon light sources that can be used in tandem with the pedagogy.

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Teaching the Subtleties of Entanglement via the Delayed-Choice Two-Slit Experiment with Polarizers

  • Leanne Doughty,
  • James K. Freericks

摘要

In instruction, most discussions about entanglement start with either the Einstein–Podolsky–Rosen experiment, or Bohm’s variant of it with spin. This introduces an extra issue related to signaling, causality, and “spooky action at a distance.” Often students focus primarily on these extraneous issues and miss the basic properties of entanglement, in particular the way a product-state superposition displays interference effects, but entangled superpositions do not. In this work, we discuss an alternative way to teach entanglement using a two-slit experiment with crossed polarizers at the slits that provide “which-way” information destroying interference and then illustrate how one can remove “which-way” information via a delayed-choice variant. This work complements recent experimental illustrations of these setups using single-photon light sources that can be used in tandem with the pedagogy.