3 ms·

I'm curious as to how the scientists confirmed that tunneling was taking place when the atoms were not being illuminated. Does anyone know how this is typically

by flak48 11y ago

I'm curious as to how the scientists confirmed that tunneling was taking place when the atoms were not being illuminated. Does anyone know how this is typically done?

gus_massa 11y ago
I hope I understood your question correctly. It's very very very difficult to take a photograph to catch the atom while tunneling. The atoms in this experiment form a lattice, and the lattice acts a trap, so the atoms can be only in some fixed spots. To go from one spot to another spot, it has to have some minimal energy, so it's equivalent to climbing a hill to go from one valley to another valley. The atom usually get that energy by random movements, but in this experiment they are very cold, to avoid this possibility, so they are trapped in one of those spots. By quantum mechanics, they can travel from one spot to another spot without enough energy. This is equivalent to going from one valley to another valley without energy to climb the hill, so the tunneling nickname. The probability is something like exp(- distance * energy_difference * constants) so it's harder to go to a spot far away and it harder to pass a tall hill (I must be missing a the time variable there, look at Wikipedia for the exact expression.) And it's exponentially harder, not jut harder. To answer your question. It's very very very difficult to take a photographs of the atoms while tunneling. If you turn off the laser and you take a photograph from time to time, you see that some atoms jump randomly from one spot to another between photos while "no one" is watching :). If you turn on the laser, the "laser" is watching, so the atoms don't move between photographs. But don't expect to get a photograph of the atoms while tunneling. EDIT: after a coffee and a shower, I changed "impossible" to "very very very difficult"
- flak48 11y ago
  I re-read the article, and combined with your answer, it makes much more sense now. What was originally confusing me, was how the scientists were confirming the presence of tunneling when the laser was off. I was mistakenly assuming that they were using some special method to infer that tunneling was taking place. But of course they don't need to, like you said. The tunneling can be inferred from the change in positions of atoms in different photographs. They don't actually need to see the actual tunneling in-progress (even if it were somehow possible/not very difficult to do so). Makes sense. Thanks for that answer, it's very helpful for someone like me whose last brush with quantum physics was the physics/chemistry courses in year 1 of engineering. Cheers

by flak48 11y ago

I'm curious as to how the scientists confirmed that tunneling was taking place when the atoms were not being illuminated. Does anyone know how this is typically done?

gus_massa 11y ago

I hope I understood your question correctly. It's very very very difficult to take a photograph to catch the atom while tunneling. The atoms in this experiment form a lattice, and the lattice acts a trap, so the atoms can be only in some fixed spots. To go from one spot to another spot, it has to have some minimal energy, so it's equivalent to climbing a hill to go from one valley to another valley. The atom usually get that energy by random movements, but in this experiment they are very cold, to avoid this possibility, so they are trapped in one of those spots. By quantum mechanics, they can travel from one spot to another spot without enough energy. This is equivalent to going from one valley to another valley without energy to climb the hill, so the tunneling nickname. The probability is something like exp(- distance * energy_difference * constants) so it's harder to go to a spot far away and it harder to pass a tall hill (I must be missing a the time variable there, look at Wikipedia for the exact expression.) And it's exponentially harder, not jut harder. To answer your question. It's very very very difficult to take a photographs of the atoms while tunneling. If you turn off the laser and you take a photograph from time to time, you see that some atoms jump randomly from one spot to another between photos while "no one" is watching :). If you turn on the laser, the "laser" is watching, so the atoms don't move between photographs. But don't expect to get a photograph of the atoms while tunneling. EDIT: after a coffee and a shower, I changed "impossible" to "very very very difficult"

flak48 11y ago
I re-read the article, and combined with your answer, it makes much more sense now. What was originally confusing me, was how the scientists were confirming the presence of tunneling when the laser was off. I was mistakenly assuming that they were using some special method to infer that tunneling was taking place. But of course they don't need to, like you said. The tunneling can be inferred from the change in positions of atoms in different photographs. They don't actually need to see the actual tunneling in-progress (even if it were somehow possible/not very difficult to do so). Makes sense. Thanks for that answer, it's very helpful for someone like me whose last brush with quantum physics was the physics/chemistry courses in year 1 of engineering. Cheers