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It probably sounds absurd, but I heard such expressions as "subtracting a particle from vacuum", or from squeezed vacuum, in the context of quantum experiments, or quantum optics, (not black holes). Can someone give me an example of situation in which a particle is subtract from vacuum? Further, if such a phenomenon is possible, are there processes made possible due to energy taken from the vacuum?

Again, classically it seems absurd, but is there any quantum process I which the answer is "yes"? (I looked at other questions that seem related, but I didn't see a sufficient analogy with mine.)

I would appreciate answers as phenomenological as possible, not formulas and formulas.

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  • $\begingroup$ Could you give a reference where that expression is used? $\endgroup$ – ACuriousMind Dec 8 '14 at 14:38
  • $\begingroup$ @ACuriousMind : unfortunately, no! In those times when I attended colloquia at Technion, such things were not interesting for me. Today when I need them, the person who said them is no more with us. But please, let this question to be visible to the community. Sometimes my questions disappear from the unanswered list (not closed, they just disappear from the unanswered list). $\endgroup$ – Sofia Dec 8 '14 at 14:45
  • $\begingroup$ @ACuriousMind: let me just say that the person who was saying such things, was faaar from being some anonymous physicist. Also, he was a very rigorous physicist, not a dreamer. $\endgroup$ – Sofia Dec 8 '14 at 14:51
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You are probably referring to the phenomenon where pairs of particles can appear and disappear randomly inside a vacuum.

Such a situation where energy is then extracted from these pairs can occur, for example, at the edge of a black hole, where a matter and antimatter pair would be created. The antimatter would go into the black hole, while the matter flies away in the opposite direction. This could decrease the mass and therefore energy of the black hole, while the mass flying away in the matter particles, creating Hawking radiation.

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  • $\begingroup$ @ Michal: thanks a lot, but it's not my case. The issue with subtracting particles was in the context of quantum experiments, they had nothing to do with black holes. But, thank you again, I will specify this restriction in the question. $\endgroup$ – Sofia Dec 8 '14 at 15:00
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Maybe what you are looking for then, is the Casimir effect??

Here, the energy in a vacuum between two plates produces a force between them.

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  • $\begingroup$ @ Michal, thanks for your attention. I will look at the issue with Casimir force, although my problem appears in the context of nuclear reactions. $\endgroup$ – Sofia Dec 8 '14 at 15:14
  • $\begingroup$ Ah, I see, I will post again if I am reminded of any other cases ;) $\endgroup$ – Michal Paszkiewicz Dec 8 '14 at 15:16
  • $\begingroup$ @ Michal : It would be great if you could give me some example closer to my context. It would help me understand a very difficult problem that I have, and for which I have no explanation. By the way, to your attention, I posted a new question in the same direction, which is probably simpler. The question is "Spontaneous de-excitation of an atom" $\endgroup$ – Sofia Dec 8 '14 at 22:32

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