'Zeno effect' verified: Atoms won't move while you watch
news.cornell.edu
news.cornell.edu
This particular effect has nothing to do with whether or not anyone is looking at an object. It's the methods of making it visible that cause the effect.
I think that a big part of the problem is trying to make the new more layman friendly removing all the math. Quantum mechanics is unintuitive but the math is very clear, so "anyone" can get the same correct result for an experiment. When you remove the math, you keep only the unintuitive part.
Another part of the problem is linkbait, making slightly wrong interpretations make more interesting articles. Sometimes there are a few articles from different news sites about some subject, and it's very common that the more misleading gets more attention here.
Sadly, my rule of thumb is https://xkcd.com/1240/
For an interesting explanation of what is happening here, I like the stack of slightly rotated polarizers. (See this comment https://news.ycombinator.com/item?id=10437289 ) The math is equivalent, but the result is not linkbaity. You can even try it at home! If you think enough about it, it's completely weird, but the calculation are pretty straightforward.
Generally a decent layman's explanation of the experiment, but they had to conflate quantum mechanics with magic by saying "the atom knew it was being watched..."
It's very hard to handle these misconceptions once they're already so widespread.
Calling printf can (will) change what's beyond the stack of the calling function, so if the pointer in question pointed outside the active stack, printf may have put a safer value there by coincidence.
methods of disassociating mutable objects before printing will save you from some heisenbugs
a la javascript
console.log(JSON.parse(JSON.stringify(obj))https://www.youtube.com/watch?v=sQfSm6o-KlQ
(Assuming it's correct - I'm not physicist)
For example, in the quantum eraser video referred to by the video you linked, it's said that there's an interference pattern for B when you don't measure the entangled associated photon A (and that there is one when you do measure A). That's not the case. If it was the case, we'd have a handy-dandy FTL communication mechanism.
What actually happens is that there's never a visible interference pattern for B in this experiment. Instead, you use the measurements of A to filter or split the measurements of B into two groups (e.g. Bs when A up, Bs when A down). Within each group of measurements, you'll find an interference pattern. The two interference patterns will complement each other so the sum is an apparent lack-of-interference; you need the As to do the separation.
I personally think the the quantum eraser experiment has a terrible misleading name. It's more of a "use entangled measurements to find the interference" experiment.
So, by measuring more and more frequently, you can effectively stop a system like that from transitioning between states.
It's an interesting example of measurement unavoidably affecting quantum systems, where the problem clearly isn't due to kicking or perturbing the state.
o
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The ball will slowly start rolling down one or the other side of the slope (because gravity).
You have a robot hand that keeps checking if the ball is still on top by grabbing it and then releasing it right in the middle. There is some leeway when the hand grabs the ball but none when it releases it.
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| o | => |o|
Is this a good analogy?
A better example might be... a series of polarizing filters? If you have a series of polarizers but skip all the way from vertical to horizontal with nothing in between, no light gets through. If you put a diagonal polarizer between the horizontal and vertical, some light gets through. If you have a big long series of very gradual steps from vertical polarizer to horizontal polarizer, almost all the light gets through. More frequent measurements causing the zeno effect is like to adding more gradations of polarizer direction causing the all-light-gets-through effect.
EDIT: On second thought, it might just be you wording making it seem weird. The analogy works if you don't look at the whole stack, but the after adding each polarizer. Still, the same effect is had as simply gradually rotating the 2nd polarizer.
Following a vertical polarizer with a horizontal polarizer will block all light. But putting a diagonal polarizer in between will result in some of the light getting through. You can find videos and explanations of this effect on youtube [2] [3].
EDIT: not that this makes the quantum effects any clearer ;)
Despite the misleading title, I imagine affecting the quantum behaviour of atoms with lasers has all kinds of nice use cases!
Now 'classical systems' are systems made of so many elements that we can only make statistical statements about it because we can't ever determine the state of each of it's constituents.
I suspect for some time now that this is also the source for the "quantum randomness". In principle, everything is deterministic, but to observe something we always have interactions with a "big classical system" (in the end it's always our brain). And because we don't know the exact state of those systems but only statistical averages, quantum mechanics looks random for us, even if it's perfectly deterministic in itself. But that's my personal view of the matter.
One of the postulates of QM is that after a measurement the system is in a well-defined state (the one we measured). But this is aphysical.
It's an artifact of the deliberate choice to formally model measurement in a way that simultaneously recognizes that all measurements disturb the measured system, while also wanting to abstract away the particular hardware used.
So, I'm starting to see wavefunction collapse and the whole Copenhagen interpretation as artifacts of the the formalism, not any kind of physical truth.
One way to do a partial measurement is to make the conditional effects less orthogonal to each other, e.g. cause a target qubit to conditionally rotate by 22 degrees instead of a full 180 degrees.
Another possible concept for a partial measurement is not distinguishing between all of the cases. For example, if a system can be in the x=-1, x=0, or x=1 cases then it's possible to do a measurement that distinguishes x=-1 from x in {0,1} without collapsing all the way down to x=0 or x=1.
So anything related to light then as well?
Same thing goes for many things, for example letting some hydrogen gas out of a gas bottle: The gas will never go back into the bottle by itself (even if there is a very very small probability that this may happen, in practice it never will). Because the behavior of this kind of systems is described in thermodynamics those systems are called "thermodynamically irreversible".
In the end it simply means that its much more easy to break things than to assemble them again (which also leads to the concept of the always increasing entropy).
It does NOT mean a human. It can interact with anything, another particle even.
However, not all interactions with another particle count as an observation, and I think the poster asked for a more precise description of the boundary, and why it would not be a boundary but actually appears to be a continuum.
The general public does, most explanations of the double slit experiment you can find lead people to believe that mind affects reality because the word observation confuses people into thinking consciousnesses is involved.
..and it is said most professional physicists don't believe in this 'consciousness (human or otherwise) causes collapse' Neumann-Wigner interpretation (and that of John Wheeler and Henri Stapps) and most amateurs do, but has it been tested in this way also by ruling out far out psi effects like retropsychokinesis by deleting or encrypting the data in such a way it can only be verified by a 'team' of independent artificial scientists (networked statistical software)?
The writer of this article is saying that the particles behave differently after being observed.
Perhaps that is a lie.
My point is, if it's a lie, let's call it a lie, not bad writing.
Short video on the double slit experiment for the layman:
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"
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
I haven't seen refutation of this in the article.
What I don't know is if the different quantum properties are independent of each other. If they are then presumably one would have to verify this Zeno effect on each property of a quantum particle. So maybe we can now say that the Zeno effect has been experimentally verified for two quantum properties now. Looked at this way you were both correct and incorrect.
If spin and momentum are 'connected' in that if you experimentally verify some meta-property about one it verifies it for the other (such as, in this case, observing a property of a quantum particle freezes that particle) then this has been proved True and you were correct.
Does this make sense? IANAQP.
If you send light through a chiral medium, the orientation of the polarization would normally rotate. However if you measure the polarization often enough (by putting enough polar filters that are all oriented in the same direction in between), this rotation will not occur. This experiment is rather simple since you only need a standard optical bench and not any low temperature setup.