page_title: Elitzur–Vaidman bomb tester
section_title: Part 2: The bomb
hierarchical_section_title: Elitzur–Vaidman bomb tester / How it works / Part 2: The bomb
caption_attribution_description: Illustration of the bomb in the experiment for proposed rewrite.
context_page_description: The Elitzur–Vaidman bomb-tester is a quantum mechanics thought experiment that uses interaction-free measurements to verify that a bomb is functional without having to detonate it. It was conceived in 1993 by Avshalom Elitzur and Lev Vaidman. Since their publication, real-world experiments have confirmed that their theoretical method works as predicted.
  The bomb tester takes advantage of two characteristics of elementary particles, such as photons or electrons: nonlocality and wave-particle duality. By placing the particle in a quantum superposition, it is possible for the experiment to verify that the bomb works without triggering its detonation, although there is still a 50% chance that the bomb will detonate in the effort.
context_section_description: A light-sensitive bomb is placed along the lower path.  If the bomb is good, when a photon arrives, it will explode and both will be destroyed. If it is a dud, the photon will pass by unaffected (see figure 4). To understand how this experiment works, it is important to know that the bomb is a kind of observer and that this encounter is a kind of observation. It can therefore collapse the photon's superposition, in which the photon is travelling along both the upper and lower paths. When it reaches the live bomb, or the detectors, however, it can only have been on one or the other. But, like the radioactive material in the box with Schrödinger's famous cat, upon its encounter with the half-silvered mirror at the beginning of the experiment, the photon, paradoxically does and does not interact with the bomb. According to the authors, the bomb both explodes and does not explode. This is only in the case of a live bomb, however. In any event, once observed by the detectors, it will have only traveled one of the paths.
caption: Figure 4: If the bomb is live, it will absorb the photon and detonate. If it is a dud, the photon is unaffected and continues along the lower path.
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