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Consider a quantum particle inside a 3D potential box. One can compute the pressure that it exerts on the walls, it's OK.

But what puzzles me is how do we actually measure such a pressure? If we take any macroscopic system with a single particle inside, the pressure will be negligible. Taking many particles forming a gas would make this too far from the ground state, so it's not really quantum (in the quantum regime this would no longer be a gas). Taking something like a semiconductor quantum dot seems to make pressure measurement unrealizable, because the dot walls are very strong, and there's much more deformation because of lattice constant mismatch than because of electron pressure on the walls.

So, what would be a realizable experiment to measure the pressure of a quantum particle, confined in the box, on the box walls?

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One could probably measure the light pressure of a photon gas on a pair of parallel mirrors. Experimentally that's on the order of 1e20+ particles in a relatively small setup with two dielectric mirrors and a laser. The resulting force should be around 1e-7N, which is easily measurable.

Would you accept that as an implementation, or are you looking for an atomic physics experiment?

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  • $\begingroup$ In principle, this counts, but I'd rather consider some particle like electron or an atom than photon, so as to remain in non-relativistic domain. $\endgroup$ – Ruslan Sep 9 '14 at 7:36
  • $\begingroup$ That's what I thought. My gut feeling tells me, that one shouldn't try to use charged particles, since the electromagnetic interaction will overwhelm the effect. But some kind of atomic fountain may work. I'll think about it, if nobody else has a concrete suggestion. And then there is the Casimir effect, for a qed variation of what you are looking for... $\endgroup$ – CuriousOne Sep 9 '14 at 7:41

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