Slashdot Mirror
Collapse of Quantum Wavefunction Captured In Slow Motion
ananyo writes "It is the most fundamental, and yet also the strangest postulate of the theory of quantum mechanics: the idea that a quantum system will catastrophically collapse from a blend of several possible quantum states to just one the moment it is measured by an experimentalist. Researchers have now been able to capture that collapse through the use of weak measurements — indirect probes of quantum systems that tweak a wavefunction slightly while providing partial information about its state, avoiding a sudden collapse. Atomic and solid-state physicist Kater Murch of the University of California, Berkeley, and his colleagues performed a series of weak measurements on a superconducting circuit that was in a superposition — a combination of two quantum states. They did this by monitoring microwaves that had passed through a box containing the circuit, based on the fact that the circuit's electrical oscillations alter the state of the microwaves as they pass through the box. Over a couple of microseconds, those weak measurements captured snapshots of the state of the circuit as it gradually changed from a superposition to just one of the states within that superposition — as if charting the collapse of a quantum wavefunction in slow motion."
So don't bother unless you want to read a dry paper.
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
IT'S A SPACESHIP!
"Catastrophically collapse", really? What's catastrophic about it?
Correlation does not imply causation
I thought that this "waveform collapse" stuff was an illusion on our part, signifying a certain lack of understanding.
Ezekiel 23:20
Is it possible that two directly inverted waveforms could coexist within universal space, by it photon energy, radio waves, or atomic vibrations?
Cheers; /-Ian/@minusian
I immediately pictured a scientist who slowly raised his hand, while shouting: nnnnnnnnnnnnoooooooooooooooooooooooooooooooooooooooooooo!!!... as the wave function collapsed.
Definitely possible.
'Wavefunction collapse' is how the Copenhagen Interpretation 'explains' this phenomenon, but like many of its 'explanations' they don't provide a compelling reason for things to happen this way. Terms like 'measurement' go from a precise QM meaning (eg. matrix multiplication) to a vague, ambiguous meaning like 'a concious observer'. This leads to tenuous extrapolations and conclusions, like the distinguished position of observers, the inclusion of conciousness into the interpretation and all the quantum 'explanations' of consciousness which that has spawned.
Alternative interpretations are much less mysterious. For example, the Many Worlds Interpretation explains it via information transmission. A measument is anything which transmits information from inside the system to outside the system. When a system is measured, it doesn't 'collapse' into one state; rather, the thing which performed the measurement becomes part of the (now larger) system.
The Transactional Interpretation explains it as two-way communication between events at different times; a measurement is any event which propagates information back in time and a system is only in multiple states because the event which caused it is awaiting the information from the measurement.
Schrodinger's cat can be used to point out the difference:
The Copenhagen Interpretation says that the cat is literally both alive and dead at the same time in the box, then when a concious observer (a human) opens the box, the cat immediately becomes either alive or dead. This is very strange, for example why is a concious observer necessary?
The Many Worlds Interpretation says that the cat is literally both alive and dead at the same time in the box. Anything which interacts with it, for example photons of light, will become part of the system; ie. the light will literally be both a reflection of a living cat and a reflection of a dead cat. If those photons enter my eye then I will literally be both a human who has seen a living cat and a human who has seen a dead cat. If you talk to me, you will literally be a human who has talked to a human who has seen a living cat and a human who has talked to a human who has seen a dead cat, and so on. This propagation is exactly the flow of information between systems; there is nothing magical about humans, except that we happen to be human. A photon would get the same results as us if it repeated our experiments, with no 'concious observer' involved, except for the fact that photons don't tend to perform experiments (ie. the 'conciousness' part of Copenhagen is an anthropic bias).
That seems a little harsh on everyone from Canada, Mexico, Brazil etc.
You're a temporary arrangement of matter sliding towards oblivion in a cold, uncaring universe
Beam me up!
Do you realize what this means?! We can finally make a cat that's dead or alive to an arbitrary percentage!
That was supposed to be "... but physicists are more mixed."
I think instead, I just witnessed in real time the catastrophic collapse of a website due to the famous "slashdot effect", first theorized circa 1997.
This is not the non-local collapse which some QM physicists (mystical school of thought) believe in. Everything in this experiment is local, the two superposed wave components which collapse into one are fully overlapped. Hence it is no more mysterious than your radio antenna collapsing superposed waves of thousands of radio stations striking it, into one component, that of a station you tuned in.
The real controversy is about existence of non-local collapse i.e. when two components and detectors are "far apart" (at space like distance), so that detection by detector D1 (supposedly) instantly collapses the remote field component causing the remote detector D2 to fail to detect it. Most recent experiment claiming to demonstrate such phenomenon with photon on a beam splitter actually cheated (see discussion here). In that claim they basically tweaked the timings on two coincidence circuits well out of manufacturer's specs so that they could never trigger D1 and D2 simultaneously.
Non-local collapse, which was never demonstrated empirically, does not follow from the Quantum Field Theory (discussion here) but is merely a hypothesis in the QM "measurement theory", which is the speculative, soft and fuzzy, part of the theory that has been debated among physicists, philosophers and mystics for nearly a century without getting anywhere so far.
Then call it US Football!
Sig?
This is silly. Taking a measurement of the microwaves that passed through it doesn't change that it was modified by the measurement. They're just using the excuse that the microwaves weren't theres, and then ignoring the fact that the microwaves were changing the process themselves.
The fact that the microwaves behaved differently is a direct result of their interaction with the wave function. Both were modified by the interaction.
They still didn't measure quantum collapse without effecting it, they're just ignoring the effect. They used microwaves to directly measure it, but just ignore that the microwaves passed through it.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
As I'm in the UK, I'd prefer to call it American-style HandEgg. Football is a game played using a (round) ball and predominately using your feet.
You're a temporary arrangement of matter sliding towards oblivion in a cold, uncaring universe
You know in games like Call of Cthulu, or more germane, games like Delta Green or Cthulutech, where doing research into 'extra dimensional science' or whatever other terms they use to describe the eldritch magics and alien geometries, drives the researchers insane?
That's what quantum physics is like.
Vintage computer games and RPG books available. Email me if you're interested.
Wow! A brit with some wit. You sir, are a credit to your island race. Say hi to the queen for me.
P.S. Ties in the unAmerican football are poorly solved. Take notice that in American football it is called SUDDEN DEATH! while in unAmerican football it is called kickball, and without surprise, the only time unAmerican football is more exciting than, say, American baseball, though only or a triffle few seconds. But it may be the only score in an otherwise very long sit, so something to go to the pub and fight about later. Fights by the fans against the other fans? No wonder there were two world wars started over there.
Cricket. Now there is a sport no one anywhere understands. Maybe the cast of Monty Python (excluding that Americam).
http://www.youtube.com/watch?v=DfPeprQ7oGc
A quote from the comments (saves time):
jon manock 1 week ago
"this video is extremely misleading. the electron does not know it is being observed and decide to behave like a particle.
it is the electron interacting with the test equipment that collapses the wave function. consciousness has nothing to do with it."
You can not tell the difference between particles that are in a superposition of states and those that have "collapsed". If such a difference could be discerned then entangled pairs could be used for faster-than-light communication by modulating their "collapsedness". These guys are not dealing with particles but a somewhat larger system. Is it an example of macroscopic system exhibiting quantum behavior? If so, does it offer a non-magical explanation of the phenomena?
Are you familiar with the work of Yves Couder? Macroscopic Newtonian systems exhibiting features of quantum behavior. All this voodoo is probably just a lack of understanding.
or it didn't happen
I'll let you in on a secret - Cricket isn't real: we just make that up to confuse non-brits.
And, since when did we start the world wars? I'm pretty sure it was Germany that did that as we only start wars with France (or places with lots of oil).
By the way, queenie says "Hello" back to you.
You're a temporary arrangement of matter sliding towards oblivion in a cold, uncaring universe
I play football with a ball shape like a foot, you know, the football.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
That's ironic, my foot is shaped like an american football.
You're a temporary arrangement of matter sliding towards oblivion in a cold, uncaring universe
I couldn't figure out if this was awesome or total BS until I RTFA.
my, your, his/her/its, our, your, their
I'm, you're, he's/she's/it's, we're, you're, they're
Google says a ball is a "a solid or hollow sphere or ovoid, esp. one that is kicked, thrown, or hit in a game." American footballs are indeed kicked, and they are spheroid. Why not change your football's name to "head sphere" since when I watch, it seems you guys bounce that sphere from your heads more often than with your foot, and in fact the foot seems to be the least used part of the bady for moving that sphere (except the hand of course).
In no way do you need a conscious observer. That's what woo and people misudnerstanding what observation think it is. All it means at the absic level is that there is an interraction to a measured system by a quanta. "This is very strange, for example why is a concious observer necessary?" because it isn't. The shroedinger cat was a way Erwin wanted to show how you can itnerpretation on the macroscopic level and push it to the absurd (crank it up to 11). Asd for the Many world interpretation you bungled it out. The MWI is that in OUR universe the wave function collapsed to A, but in another it collapsed to B. There is NO communication between universe. It just happens that this was how the measurement turned out in our universe.
Okay, I'll start calling soccer "head sphere" if you start calling american football "hand ovoid".
Also, why are toilets called "rest rooms"? I prefer to call them "thinking rooms" as it's where a lot of people come up with good thoughts.
You're a temporary arrangement of matter sliding towards oblivion in a cold, uncaring universe
That's a fallacy, not a physic argument. MW violate other physic principle anyway. Like parity.
This is GREAT! I have always wanted to see the "Collapse of a Quantum Wavefunction".
Lubos Motl is in this case arguing against a straw man. He starts by assuming you have an electron in a superposition of two states, and then goes on to prove that the expectation value of observing it in both states at the same time is zero. Nothing is controversial about that, and because interpretations of quantum mechanics are mathematically equivalent, they all predict that.
Many worlds has two ingredients: 1. Superpositions, which is a basic building block of quantum mechanics, and 2. not treating observers specially, not exempting them from entering into superpositions themselves.
The many worlds interpretation of his proof, where he valiantly destroys his straw-man, would say that after measuring the spin of the electron, the observer would be in an entangled superposition with the electron. Just like the electron is in a superposition of having spin up and down, the observer would enter a superposition of having observed spin up and having observed spin down. And because this is an entangled superposition, each version of the observer would keep getting the same result if he repeats his experiment. They would both see only a single spin no matter how many times the observe it - the probability each to observe two different spins is zero. This is the probability Motl computed in his straw-man proof. Ans it is perfectly consistent with many-worlds, and with any other interpretation of quantum mechanics. Since the only are interpretations, after all. The physics is in the math, which they all have in common.