P09.00010. Diffraction-Based Interaction-Free Measurements

Presented by: Spencer Rogers


We consider the problem of determining if a single-slit contains a bomb in its middle region using a single photon test. We notice that the quantum case allows the bomb to significantly increase the probability for the photon to reach certain detection positions, in particular the dark bands of the single-slit pattern. The bomb's presence can be inferred without exploding it when the photon lands at one of these positions. We thus find a diffractive extension to the interaction-free measurement protocol of Elitzur and Vaidman. In addition, we consider the role of time in interaction-free measurements. We find that, if the bomb is thought of as a measuring device which checks periodically if the photon is in its space, then it can only find the particle (and "explode") if its measurement rate is finite. The alternative is the Zeno limit, where the bomb acts like an infinite potential barrier. Critics of interaction-free measurement may find it interesting that the normal, non-Zeno bomb can be passed through without setting it off.


  • Spencer Rogers
  • Yakir Aharonov
  • Cyril Elouard
  • Andrew Jordan


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