Quantum Measurements Leave Schrödinger's Cat Alive

I want a refund, Slashdot by Anonymous Coward · 2012-10-03 16:31 · Score: 4, Funny

The SchrÃdinger's Cat I bought from Think Geek keeps dying half the time.

Re:I want a refund, Slashdot by mcgrew · 2012-10-04 02:30 · Score: 2

I prefer Schrödinger's Fridge.
I don't know if everyone is joking (well, the cartoonist who drew that linked cartoon isn't serious) or everyone misunderstands the concept that whoever does the Bob cartoons is poking fun at. It simply means "you don't know unless you test". The idea that a cat is both alive and dead is ludicrous.

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Re:I want a refund, Slashdot by Mr.+Slippery · 2012-10-04 03:18 · Score: 1

The idea that a cat is both alive and dead is ludicrous.
That was Schrï½dinger's point with the cat example, it was meant as a refutation of certain ideas about the interpretation of quantum physics.
But the fact that something is "ludicrous" to our intuition doesn't mean it's not true.
The question of how to interpret quantum physics -- what "reality" the various mathematical artifacts possess -- remains open, and may be more of a philosophical one about what we agree to call "real" than something that can be resolved by physics.

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Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 16:32 · Score: 0

Why is it equivalent of peeking without killing it ?!

The cat might already be dead when you peek. Now, apparantly you simply can peek at the cat's state.

Re:Equivalent of peeking without killing it ?! by Sun · 2012-10-03 16:36 · Score: 4, Insightful

Why is it equivalent of peeking without killing it ?!
The cat might already be dead when you peek. Now, apparantly you simply can peek at the cat's state.
I think you missed the whole point of the thought experiment. No, the cat is decidedly not already dead when you peeked. It is the moment of your peeking that picks a state for the cat.
Which, of course, means that the summary is meaningless. I'll go read TFA, and, more likely, then consult with a Physics Phd I know to try and make (relative) sense of this discovery.
Shachar
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 16:46 · Score: 5, Informative

This is the equivalent of weighing the box. By not opening the box you don't collapse the wave function. Instead you measure some other property that is independent of the wave function. It is nothing like peeking in the box, nor does it gain any information from the wave function.
Re:Equivalent of peeking without killing it ?! by Intropy · 2012-10-03 16:47 · Score: 3, Insightful

I think perhaps you may be the one confused. The point of the thought experiment is that you cannot know whether the cat is alive or dead before opening the box. It's 50/50. In one interpretation of quantum mechanics that means that the cat exists in a combination of both states prior to observing it. Observing it causes one or the other of the states to prevail.
Re:Equivalent of peeking without killing it ?! by Black+Parrot · 2012-10-03 17:09 · Score: 3, Interesting

I always wondered why the cat didn't qualify as an observer to begin with.

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Re:Equivalent of peeking without killing it ?! by Nostromo21 · 2012-10-03 17:33 · Score: 0

So it's like deducing if the cat is alive by listening very closely if any sound is coming from the box; or measuring minute vibrations from it, or perhaps even using IR to measure the body heat through the cardboard...? Ok, we're stretching metaphors a bit far now, BUT, is it possible with QM that the cat is actually *dead* to begin with (if that even makes sense for any solution of the wave function) AND you then bring it back to life by observing/interacting with it...?
Re:Equivalent of peeking without killing it ?! by Sun · 2012-10-03 17:35 · Score: 4, Interesting

The point of the thought experiment is that you cannot know whether the cat is alive or dead before opening the box.
No, that is not the experiment's point. That is its premise.

It's 50/50. In one interpretation of quantum mechanics that means that the cat exists in a combination of both states prior to observing it. Observing it causes one or the other of the states to prevail.
It is the only interpretation that I am aware of (though its precise phrasing varies). In fact, it is the only reason that anyone hopes qbits will work. Hence me not being confused.
Unlike what the original poster said, the cat is not already dead when you open the box. That is the whole point of the experiment. The cat is neither alive nor dead until the point in time in which you look, at which point it has already been alive/dead all along.
This principle is the one that drives the quantum computing research. The idea is that you create 512 qbits signifying a number. Since they are in their base form, they each can be either 1 or zero, which means that they are, potentially, all 2^512 possible numbers. You then pass them through a series of filters that, essentially, force them to multiply with another set of 512 qbits and form a known result. Only then do you check what each of the qbits is. You have just factored a 1024 bit integer in zero time by letting quantum mechanics test all possible combination concurrently.
Shachar
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 17:37 · Score: 1

AFAIK it does, which is why this experiment wouldn't *actually* work. From what I have gathered about the topic, an "observer" is any VERY-many-particle system (read: billions of billions of degrees of freedom) that interacts with the quantum system. Introdouce that many degrees of freedom and the superposition is gone.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 17:37 · Score: 4, Insightful

Not exactly. A cat in such a situation would of course be dead or alive, regardless of whether you observe it or not. You may not know *whether* the cat is alive or dead, but you know *that* the cat is alive or dead. The measurement of the state to choose whether or not to kill the cat would in itself collapse the waveform.
Schroedinger developed the thought experiment to describe what he considered the absurdity of the Copenhagen interpretation of quantum mechanics. It's not meant to be taken as literally as it is tended to be.
Re:Equivalent of peeking without killing it ?! by Sun · 2012-10-03 17:44 · Score: 2

No. You cannot measure whether the cat is alive without causing a determination of that very question. You can measure other things, though.
I should point out that the cat analogy is not a very good one, and TFA chose it only to make the article more appealing.
Shachar
Re:Equivalent of peeking without killing it ?! by Dahamma · 2012-10-03 17:45 · Score: 1

But weighing the box won't tell you anything (no, a cat's soul does NOT weigh 21 grams). I think it's more the equivalent of smelling the box.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 17:45 · Score: 1

There are a lot of replies that seem to be missing it. If you measure quick enough after closing the box with the cat in it, the chances of it being dead versus alive are not 50-50. Since it was alive when you closed the box, there would be a really high chance it is still alive when you peak if you peak much quicker than the halflife of the decay process that is supposed to trigger the death (for the version that uses a decay particle as the source of chance). Since this peeking collapses the wave function back from a 99-1% split back to 100% alive state, you can keep doing this to keep collapsing it to the alive site with very high probability. In the right conditions, you can go from what was a 50% chance of it being dead after a certain amount of time, to a vanishingly small chance if you can keep measuring quick enough. The actual states of a cat are much more complex, but there are two state quantum systems that take a certain amount of time to evolve into a superposition of both states.
Re:Equivalent of peeking without killing it ?! by Sun · 2012-10-03 17:53 · Score: 2

Not exactly. A cat in such a situation would of course be dead or alive, regardless of whether you observe it or not. You may not know *whether* the cat is alive or dead, but you know *that* the cat is alive or dead.
The experiment doesn't work, so you are right. But had the experiment worked, then that claim would be incorrect. The point in time in which the universe decides whether the cat died or not is when we test it, not before. If we never test the cat, it is neither alive nor dead.

The measurement of the state to choose whether or not to kill the cat would in itself collapse the waveform.
Exactly. It is uncollapsed before the measurement.

Schroedinger developed the thought experiment to describe what he considered the absurdity of the Copenhagen interpretation of quantum mechanics. It's not meant to be taken as literally as it is tended to be.
But that interpretation prevailed. That is the whole point of ESR. It is not possible to extend a wavelength function, uncollapsed, to the size of a cat, but when actual atoms are involved it really is the point of testing that determines the result. The result is not there all along, just waiting to be measured.
Shachar
Re:Equivalent of peeking without killing it ?! by Intropy · 2012-10-03 17:58 · Score: 4, Insightful

It's 50/50. In one interpretation of quantum mechanics that means that the cat exists in a combination of both states prior to observing it. Observing it causes one or the other of the states to prevail.
It is the only interpretation that I am aware of (though its precise phrasing varies).
There are many other interpretations. The one where it exists in a combination of the possible states is the Copenhagen interpretation.
Another popular one is the many words interpretation. Instead of the cat being in a combination of the possible states, there are multiple universes with each universe containing a different possible history (dies at T=1, dies at T=2, still alive, etc.) and there is a different version of the observer in each universe coming to a conclusion based on which universe he's in.
In the relational interpretation observer 1 could take a peek, and know the cat is dead, while for observer 2, who hasn't peeked, the cat is still in both states.
In the ensemble interpretation the cat is definitely either alive or dead, you just don't know which before making the observation. The probability distribution does not apply to a single cat, but rather to an ensemble of cats. Repeat the experiment 1000 times and you'll get about 500 alive and 500 dead.

Unlike what the original poster said, the cat is not already dead when you open the box. That is the whole point of the experiment. The cat is neither alive nor dead until the point in time in which you look, at which point it has already been alive/dead all along.
That interpretation is different from "the only interpretation [you] are aware of." As I said above the interpretation Schrodinger was discussing has the cat in a combination of both states. Not that it's not in "neither" state. It's in a combination of them. The AC above was pointing out that you might not be keeping the cat alive while peeking. You might be peeking while keeping the cat dead. Or as the article rather than the headline actually says, you get to peek and keep it in the superposition without collapsing it.
Re:Equivalent of peeking without killing it ?! by sFurbo · 2012-10-03 18:20 · Score: 4, Interesting

It is the only interpretation that I am aware of (though its precise phrasing varies).

That is the Copenhagen interpretation. There are several others: In the many-world interpretation, there are universe in which the cat is alive, and universes in which the cat is dead. Until you open the peek, you can interact with both. Ones you have peeked, the versions of you in the universe where the cat is dead and the versions of you in the universe where the cat is alive diverges, and cannot interact anymore (roughly). Then there is the de Borglie-Bohm interpretation, where the cat is either dead or alive (particles have a definite, deterministic position), but until you have observed it, you can only interact with the wavefunction, which is the same for dead and alive cats (I think, but I might have horribly misunderstood it). In fact, there a quite a lot different interpretations of quantum mechanics

In fact, it is the only reason that anyone hopes qbits will work.

Qubits works because of quantum mechanics, that is, because the equations are as they are. That have nothing to do with the interpretation, which is how we understand the equations. Interpretations are not scientific, as they make exactly the same predictions as the underlying model, but are more complex. They are not really needed, but the human mind doesn't like thinking in equations, it prefers to have something that behave like something physical, so we like having them.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 18:28 · Score: 0

Combining quantum mechanics and relativity ... maybe from the cat's point of view, it is alive, but it isn't sure whether you are alive or dead until it escapes from the box.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 18:32 · Score: 0

The experiment doesn't work, so you are right. But had the experiment worked, then that claim would be incorrect. The point in time in which the universe decides whether the cat died or not is when we test it, not before. If we never test the cat, it is neither alive nor dead.
That... is an absolutely lovely bit of double think. Admit the experiment doesn't work, then spend the rest of the post arguing the point based on what it would mean if it DID work.
Re:Equivalent of peeking without killing it ?! by WaffleMonster · 2012-10-03 18:37 · Score: 1

I think you missed the whole point of the thought experiment. No, the cat is decidedly not already dead when you peeked. It is the moment of your peeking that picks a state for the cat.
The worst ever "thought experiment" by far is Schrodinger's cat. To say a living cat was ever in a superposition of alive or dead is wrong and stupid. These words only confuse people unecessarily.
No cat was never a participant in any coherent quantum system only the measuring device which **triggers** death of the cat had anything to do with the quantum system.
Asking if a tree still falls in the forest if nobody sees it is about as instructive as the cat in the box analogy.

Which, of course, means that the summary is meaningless. I'll go read TFA, and, more likely, then consult with a Physics Phd I know to try and make (relative) sense of this discovery.
Nothing at all has been "discovered". All they did was physically implement something for which the properties have been calculated and well understood for many many decades.
Re:Equivalent of peeking without killing it ?! by daffy951 · 2012-10-03 18:40 · Score: 1

The point in time in which the universe decides whether the cat died or not is when we test it, not before. If we never test the cat, it is neither alive nor dead.
Uhm.. No? The point in time the cat died is exactly that point in time, whenever we test it? If we never test the cat, it's *either* alive or dead..
Re:Equivalent of peeking without killing it ?! by WaffleMonster · 2012-10-03 18:55 · Score: 4, Insightful

In one interpretation of quantum mechanics that means that the cat exists in a combination of both states prior to observing it.
The only thing in any sort of superposition is the measuring device. The hammer which breaks the beaker of cat poison, the beaker breaking and the cat dieing are not part of the superposition. They are all separate events but whatever it all sounds much better if you make mystical claims.

Observing it causes one or the other of the states to prevail.
No it is "disturbing" not "observing" ... just more unecessary mysticism to make understanding basic ideas seem more difficult than they actually are.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 18:57 · Score: 1

Unlike what the original poster said, the cat is not already dead when you open the box. That is the whole point of the experiment. The cat is neither alive nor dead until the point in time in which you look, at which point it has already been alive/dead all along.
The Copenhagen interpretation of quantum mechanics is what made Schrödinger come up with that thought experiment to begin with. It is also what made Einstein say that God doesn't play dice with the world. (he was a firm believer of determinism.)
The cat thought experiment was Schrödingers way of being a bit of a sensationalist (I guess that is why the idea got so much publicity.) in that the claim is that if we follow the Copenhagen interpretation and say that the particles are in all possible states before measurement, even if we are just talking about a single particle, we can quickly get a situation where we can no longer differ between life and death. Obviously this is silly, the cat can't be both alive and dead, instead Schrödinger would have preferred an interpretation where the state just is unknown rather than all states at once.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 19:07 · Score: 0

Ok, we're stretching metaphors a bit far now, BUT, is it possible with QM that the cat is actually *dead* to begin with (if that even makes sense for any solution of the wave function) AND you then bring it back to life by observing/interacting with it...?
No, the thing that makes the Copenhagen interpretation so controversial is that with it the cat is both alive and dead at the same time, the cat thought experiment was made by Schrödinger to highlight the absurdity of the Copenhagen interpretation, something can't be both dead and alive at the same time but if we assume that something can have several quantum states at once that is the natural extension of it.
The full thought experiment includes a living cat, a vial of poison and a radioactive particle what can trigger the poisoning of the cat. If the particle is in all states then it will both poison the cat and not poison it and the outcome is determined by opening the box. In determinable physics the cat is already dead or alive before opening the box and we only find out about the result upon opening.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 19:28 · Score: 0

Or as the article rather than the headline actually says, you get to peek and keep it in the superposition without collapsing it.
As the article says, in order to continue to use the Cat-based thought experiment we must consider in the original experiment that the box was either completely open or completely closed, and they've found a way to only open it partway- you are only getting a limited view of the cat's state but that they have found a way to infer its state and then close the box again, allowing the cat to remain "both alive and dead".
Anyhow, it's just a thought experiment.
Re:Equivalent of peeking without killing it ?! by someone1234 · 2012-10-03 19:39 · Score: 0

You know the cat is alive. But opening the box has 50% of killing it.
If the cat can "measure" the quantum state by its death, then it counts as "opening the box" too.

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Re:Equivalent of peeking without killing it ?! by petes_PoV · 2012-10-03 19:48 · Score: 5, Interesting

Meh, it's already been done experimentally
Have a look at the Quantum Zeno Effect which is both one of the scariest and most awesome pieces of experimental quantum physics around. Just in case your Google is broken, the experiment stops the random decay of unstable particles by continually measuring their state. Since the cat is just an allegory for these sorts of particles, the experiment has already been done - yes you can prevent a random (quantum) event by taking continuous measurements.
You don't need this thought experiment any more - as *real* physics cruised past these mind games decades ago.

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Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 20:47 · Score: 0

nor does it gain any information from the wave function
Apart from measuring its frequency. It's nothing like weighing the box; they interact with the wave function. RTFA, and that goes for the modders who gave this +5 Informative (I guess wrong information is still information, though).
Re:Equivalent of peeking without killing it ?! by hajus · 2012-10-03 20:57 · Score: 1

These interpretations all are similar in their measurable outcomes. That's why we have these interpretations instead of focusing in on one of them.
The many worlds postulate, for instance, doesn't split the universe into many until the observation is made. So the cat is in a multi-state until that point in time. In all the interpretations, there is a multi-state until the measurement is made and then something happens, depending on the interpretation.
Re:Equivalent of peeking without killing it ?! by Stuarticus · 2012-10-03 20:59 · Score: 2

"It's a bit like watching your kettle, to make sure it never boils"
Geordi La Forge

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Re:Equivalent of peeking without killing it ?! by Guignol · 2012-10-03 21:12 · Score: 3, Informative

If the cat was just either dead or alive (according to whether or not the gun, or poison or whatever was triggered by some beta decay) and we would just be unaware of it until opening the box
What would be wrong about it ?
You put a coin in a box, shake the box. surely, it is either head or tails, you just know what it is when you open the box
So why do you think there is such a buzz around the Schrödinger’s cat ?
Precisely because, the experiment is setup so that the cat is not either alive or dead, but in a special state
Schrödinger put together this thought experiment to show how silly the Copenhagen interpretation was (to his eyes)
The experiment is there to say "according to you, the cat is both dead and alive (which we can all agree on is ridiculous)"
Except it's not that simple, and then, there is entanglement and there indeed are "weird mixed states"
Re:Equivalent of peeking without killing it ?! by expatriot · 2012-10-03 21:48 · Score: 1

The cat is alive or dead and not ever in a state of superposition.
The example was (I hope intentionally) chosen to illustrate how poorly our macro world and macro thinking fail at the quantum level.
If you have any doubt of this and are romantically tied to the "alive and dead" cat, consider this: The cat is capable of making an observation. It is a complex collection of moving parts. If the parts stop moving, that is an observation.
It may be the case that quantum states on small particles do not have any internal world. That is a large area of discussion in physics. Is quantum mechanics the result of a hidden (to us) world that follows reasonable laws, or is it just very weird all the way down.
Re:Equivalent of peeking without killing it ?! by Nerdfest · 2012-10-03 22:21 · Score: 1

Does this method of observing really change anything? To me, it doesn't unless they can actually measure it, find it dead, measure again, the find it alive. If the observation is still fixing the state, in what way does this help? I will add here that I an not a quantum physicist,I did not RTFA, and it's 06:00. (That sounds like the SlashDot equivalent of that line towards the end of the "Blues Brothers").
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 22:34 · Score: 1

They are not really needed, but the human mind doesn't like thinking in equations, it prefers to have something that behave like something physical, so we like having them.
Exactly. A workable interpretation would be that since the equations work that the world is in fact just those equations. Values are simply undefined until you plug in the values for the other variables.
But we're evolved to our experience of the real world, so want the real world to be 'real' and equations only to describe how the real world worlds, not be it. So we reject that idea instinctively.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-03 22:46 · Score: 0

Or shaking it and listening for a 'meow'
Re:Equivalent of peeking without killing it ?! by Jamu · 2012-10-03 23:37 · Score: 1

It follows from the formulation of Quantum Theory. The state of any system can be described by a superposition of, one of more, state vectors. The cat's initial state can be described as a superposition of the vectors associated with its final states: Alive and Dead.

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Re:Equivalent of peeking without killing it ?! by baffled · 2012-10-03 23:38 · Score: 1

Qubits works because of quantum mechanics, that is, because the equations are as they are. That have nothing to do with the interpretation, which is how we understand the equations. Interpretations are not scientific, as they make exactly the same predictions as the underlying model, but are more complex. They are not really needed, but the human mind doesn't like thinking in equations, it prefers to have something that behave like something physical, so we like having them.
The equations are derived through observation of physical reality. The equations are a construct of our minds that allow recognized patterns to provide predictions of physical reality. The interpretations are arguably more accurate than the equation, as they can possibly identify conditions the math has yet to be 'adjusted' to account for. To discount the source of these equations - our perceptions of the universe - is foolish.
Re:Equivalent of peeking without killing it ?! by sFurbo · 2012-10-03 23:53 · Score: 1

Aren't you confounding interpretations with observations? Interpretations are interpretations of what the equations say, so they can't be more accurate than the equations. I am not discounting the interpretations, they are extremely helpful in making us understand what the equations say, and wondering about them might give rise to new hypothesis, which can be tested, but that doesn't make the interpretations themselves scientific.
Re:Equivalent of peeking without killing it ?! by ceoyoyo · 2012-10-04 00:09 · Score: 3, Informative

No, you don't get to peek at the cat's state. You can peek at some other property, like how fast it's transitioning between (quantum) states, but you can't see the cat's state.
To use the analogy of the thought experiment, maybe you could peek in the box and determine whether there is a cat in the box at all, or what colour it is, but if you look long enough to determine whether the cat is alive or dead then you'll destroy the superposition.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 00:10 · Score: 1

When I read the summary I also immediately thought of the quantum Zeno effect, but it's a different phenomenon.
In the quantum Zeno effect, you're preventing particles from decaying by constant measurement (and therefore causing the wavefunction to collapse).
Here, you're observing particles without destroying the wavefunction.
Re:Equivalent of peeking without killing it ?! by Type44Q · 2012-10-04 00:15 · Score: 1

I, for one, think the entirety of the above conversation should be modded "Score:5, Fucking Bewildering;" who's with me? :)
Re:Equivalent of peeking without killing it ?! by ceoyoyo · 2012-10-04 00:15 · Score: 1

That doesn't make sense. The equations of quantum mechanics describe the world, they don't create it (otherwise the world would only be a century old). We've found equations that work, but just like any equations they only tell us what's happening, not why. Newton's or Einstein's equations or the ideal gas law are no different.
Re:Equivalent of peeking without killing it ?! by Bengie · 2012-10-04 00:21 · Score: 1

If it remains in a quantum state, then it's remaining in a "random" state. If you peek and see "dead", you have a 50% chance to peek and see "alive" next time. If you peek and see dead, then keep seeing dead, then you know you have collapsed the state.

My understanding anyway.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 00:37 · Score: 1

No, this is not the quantum zeno effect. The experiment in the article is about quantum weak measurement. The idea is the measurement does not return the maximum possible (or as I will call it "full") information about the system, and since full information is not extracted, the state is only partially disturbed by the measurement. The quantum zeno effect, on the other hand, involves full measurement and complete state projection to keep the state from evolving. These two topic are rather different.
Of course, quantum weak measurement has also been done. Irfan Siddiqi at Berkeley recently used it to perform a quantum feedback circuit. And it has been done in different forms for the last 10 years around the world. The difference in this article is that the state being measured is what is known as a "cat state". A cat state is a state that has many particles with strong mutual entanglement. The entanglement makes the state very fragile to measurement, as measurement of any one particle will destroy the state.
Re:Equivalent of peeking without killing it ?! by YttriumOxide · 2012-10-04 01:42 · Score: 0

Will you fucking lemming-cunts stop modding everything up to +5 when it's wrong?
No. Because moderation is NOT about "right" or "wrong". It's about "Interesting", "Informative", "Insightful", "Funny", "Offtopic", "Troll", and "Flamebait".
Whilst having mod point, I've often disagreed entirely with what someone is saying and was quite certain that it was completely and utterly wrong. It was however extremely interesting, and so I modded it as such. As far as I can tell from reading the moderation guidelines, that is the correct thing to do.
This very post I'm now writing for example should probably get some "Offtopic" and some "Informative" mods. Maybe "Insightful" or "Interesting" if some people think so, but I personally don't.

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Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 01:59 · Score: 0

It has long annoyed me that quantum zealots take a simple (but classically unintuitive) truth and turn it into the basis of their beliefs.
Even "passive" measurements required something interacting with the target and then actively measuring the results of that interaction. Vision requires photons bouncing off (or emitted by) an object, then gatherring enough of those photons to discern meaning.
The whole thing started when trying to explain that when you are trying to measure an electron, and your only way to measure it is to hit it with an electron, you are going to alter the properties of the electron you are trying to observe.
The mathematical difference between "superposition of all possible states" and "analog state that is forced to a discrete position when tested" is nonexistant. The philosophical difference is dramatic.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 02:46 · Score: 0

If you could fully isolate the inside of the box from the outside world when it was closed, then there would be nothing wrong about discussing the cat being in a superposition. The state of the cat depends on the state of the device that is supposed to trigger its death, so it would enter superposition too. This is no different than one way to entangle particles: perform an operation that makes the state of object B depend on object A, then if object A is in a superposition, they will enter a superposition of correlated states. The cat would actually be in a superposition in the sense that if there were some operation you could do to project the cat's state on to some other state basis, you could test Bell's inequality with it (assuming you could define the states of such a complex object well enough for measurements too...). The practical limitation is that interaction with the anything outside the system (box in this case) can lead to loss of coherence, and you could lose the quantum properties of the superposition. This doesn't have anything to do with whether the cat is capable of observation or not as the poster just above this says. Experimenters have enough trouble keeping coherence in setups much, much smaller and simpler than a cat at the moment.
Re:Equivalent of peeking without killing it ?! by tgibbs · 2012-10-04 02:58 · Score: 2

There are many other interpretations. The one where it exists in a combination of the possible states is the Copenhagen interpretation.
Another popular one is the many words interpretation. Instead of the cat being in a combination of the possible states, there are multiple universes with each universe containing a different possible history (dies at T=1, dies at T=2, still alive, etc.) and there is a different version of the observer in each universe coming to a conclusion based on which universe he's in.
Many worlds does not get you away from quantum superposition, because the different histories still have to be able to interfere to be consistent with the equations. My understanding of the many worlds interpretation is that when we open the box, our state becomes correlated with the state of the cat, so that the system goes from outside scientist observing a closed box containing a superposition of live cat and dead cat, to a superposition of sad scientist observing a dead cat and relieved scientist observing a live cat. In a sense, the superposition appears to go away because we become part of it. So this is a method of obtaining information about the nature of the superposition inside the box without ourselves becoming correlated with the individual states.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 02:59 · Score: 0

No one is really sure what an observer is. In the interpretations I'm familiar with, the cat would be an observer, and from it's point of view it would either be killed or not quite definitely. But from the scientist's point of view, the cat is just part of the system, subject to the same superposition as anything else. Only when the scientist makes the measurement can they themselves be sure of the outcome. (And, if you put the scientist's whole lab inside a big sealed box, you could say that the scientist is also in a superposition of either having seen a dead cat or a live cat...)
In the many-worlds view, you could say this is because an observer is simply looking at certain branch(es) of the diverging worlds, and there's no requirement that different living beings be on the same branch. In the Copenhagen interpretation... I actually have no idea what that would describe.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 03:07 · Score: 0

An observer is just an abstraction of the world outside the system interacting with the system. In an ideal set up, like most thought experiments, the only way the system under consideration interacts with the outside is via observation. In the real world, isolating things is a huge pain, with stray E&M radiation, interaction with the container, heat, and so on depending on your particular setup. All of those interactions, whether intentional observation or unintentional interactions, have varying potential to change the state of the system you are considering, and could force it into some particular, possibly unknown, state. The unintentional interactions is basically just a source of noise, and a lot of work goes into making sure the signal to noise ratio is really high for simple systems.
For example, you could have a system that produces two entangled electrons that have opposite spins, so there is always one up and one down. In an ideal case, you would never observe both being the same. In a less ideal case, where the electrons could be exposed to stray radio waves or light from black body radiation of a containment system that is too warm, or say bump into a stray gas particle in a less than perfect vacuum, you will get some fraction of measurements where both are up or both are down due to one of those electrons hitting something.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 03:17 · Score: 0

Physics is about describing something before it happens. The point of the cat is that you can't know the result. It is where Enstien's "god does not play dice" line comes from. Quantum mechanics has uncertainty in all the calculations.
Re:Equivalent of peeking without killing it ?! by Will.Woodhull · 2012-10-04 03:19 · Score: 3, Interesting

But weakly observing it can have value. It would be possible, for instance, to determine whether there is a cat in the box at the moment (perhaps by weighing the box and comparing the finding with a predetermined minimum-weight-of-cat value). This is important because a cat that is not observed in any way may or may not be in any particular place. Anyone who has ever lived with a cat knows this. People who have never been owned by a cat may be incapable of understanding this, and probably should not look for a career as a quantum mechanic.
But that explanation might be too subtle for classical physicists (who likely do not much like cats, ever since Schrödinger soured them on the cute little beasties). So for them the dilemma can be stated in a more gross fashion: how can you even know whether a cat in the box is a part of the device you are trying to build unless you at least look at whether a box is or is not present? It would seem that some degree of weak observation is indeed necessary if anything is to be done.
The underlying problem is of course that quantum mechanics sits in the intersection of physics and semantics. It is not only the case that classical physics is unable to handle what is happening at the quantum level. It is also the case that as a product of this Universe, the human brain is basically incapable of understanding quantum level events. There's something happening here, but what it is ain't exactly clear... and never will be. So sayeth the Copenhagen convention.
I don't expect anyone on Slashdot to accept this on face value. But I do have a citation: check this out. One of the more obvious implications is that if you do not have a sense of humor, then becoming a quantum mechanic is not a good career choice for you.

--
Will
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 04:26 · Score: 0

no matter how (or when) you look at it, that's a LOT of dead cats...
Re:Equivalent of peeking without killing it ?! by Giant+Electronic+Bra · 2012-10-04 04:42 · Score: 2

Untrue, and in fact the WHOLE POINT OF THIS ARTICLE is actually to describe why the 'classic' interpretation of the Uncertainty Principle doesn't work, because it doesn't explain how you can perform certain types of measurements on a set of entangled quantum states. This would not be possible if the "changing the state" interpretation was correct. In fact what is being established here is a more exact and in some sense looser type of Uncertainty Principle. Much like Newtonian Mechanics at the limit are indistinguishable from GR, so Heisenberg's UP is at the limit virtually indistinguishable from this new version they ARE different. The whole cat thing is just an illustration of ways in which they are different. Schoedinger's Cat is a lot like in classical physics accelerating something to relativistic velocities, the old-fashioned UP breaks down, we CAN observe some properties of the cat without deciding if it is alive or dead. In the end though once we DO know that, there's no going back, you'll never observe the dead cat and then the alive cat. That is still forbidden (technically just fantastically unlikely).

--
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
Re:Equivalent of peeking without killing it ?! by toriver · 2012-10-04 04:52 · Score: 1

"50/50" is probability, you need more than one experiment to decide the ratios of the two different states. The problem is, once you have made, say 1000 experiments you have really just moved 1000 steps along a path; there are other paths you could have ended up on. So maybe you come to exactly 50/50 as the ratio, but somewhere out there in the multiverse there is a world where the 1000 experiments led to a 70/30 ratio instead. You just cannot observe it because you diverged at some point: You are not there, you are here.
Re:Equivalent of peeking without killing it ?! by Giant+Electronic+Bra · 2012-10-04 05:00 · Score: 1

That was good, you should post from an account! ;)

--
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson
Re:Equivalent of peeking without killing it ?! by strikethree · 2012-10-04 05:16 · Score: 1

Honestly, I have tried to understand the thought experiment but what I know of reality keeps getting in the way. Who cares if you KNOW whether the cat is alive or dead before you open the box? If the cat is alive, it does not matter. If the cat is dead, you can check the decomposition of the cat and know when it died. I just HAVE to be missing something here. How can the cat REALLY be both alive and dead when you can check on the exact time of death?

--
"Someone needs to talk to the tree of liberty about its ghoulish drinking problem." by ohnocitizen
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 05:24 · Score: 0

So, really, my refrigerator is a qubit, too. Too bad there's not a way to measure whether the light actually stays on when I close the door or not. Because said measurement devices obviously perturb its quantum state which forces its quantum wave function to collapse after the door is closed.
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 08:20 · Score: 0

maybe the cat just died of fucking boredom prior to collapsing the quantum intertwinglement listening to this tedious thread unfolding.
ever thought about that poindexter?
Re:Equivalent of peeking without killing it ?! by Anonymous Coward · 2012-10-04 12:27 · Score: 0

What I never understood is...
Presumably the cat itself knows if it's dying. And it knows if it's still alive. Why doesn't it count as an observer of reality?
The only way around that is to frame the experiment with some non-sentient life, such as a plant or fungus. But that kind of lessens the impact, so we're stuck with cats.
Re:Equivalent of peeking without killing it ?! by tgibbs · 2012-10-05 07:13 · Score: 1

The cat does know. The superposition is of a live cat (that knows it is alive) with a dead cat (that presumably doesn't know anything).

The cat is alive... by geoffrobinson · 2012-10-03 16:34 · Score: 4, Funny

and extremely pissed off about your experiment.

http://afternoonsnoozebutton.com/post/9395842065/breaking-news-schrodingers-cat-is-alive-and

--
Except for ending slavery, the Nazis, communism, & securing American independence, war has never solved anything.

Re:The cat is alive... by Anonymous Coward · 2012-10-04 04:37 · Score: 0

The cat starved to death long ago. Wait long enough and all quantum states will decay to unequivocally dead.

Scrodingpost by Anonymous Coward · 2012-10-03 16:35 · Score: 0, Offtopic

Slightly look at me, and I will post and no post at the same time

The suspense is killing me. by Anonymous Coward · 2012-10-03 16:36 · Score: 0

--In a large crowded stadium -- "Ladies and gentlemen, the results are finally in; the cat is in fact, ALIVE!" --- crowd erupts in applause with cheering--

Re:first post ! by User8201 · 2012-10-03 16:37 · Score: 1

Does anyone here RTFA?

The BEST related animation by Jonah+Hex · 2012-10-03 16:40 · Score: 4, Interesting

This one is as mind bending as the metaphor itself: http://www.youtube.com/watch?v=JNalMWLnt0o From the youTube description:

This animation was created for an animation show in London by the very talented Chavdar Yordanov https://vimeo.com/chavdaryordanov

Not my Work! - HEX

--
Horror & SciFi Erotic Nudes

Re:The BEST related animation by Raenex · 2012-10-04 04:56 · Score: 1

The drawings were decent (except for the hands, the mark of a great cartoonist), but I hate shitty animations that bounce around. The story itself was a simplistic revenge story and uninteresting.
Re:The BEST related animation by Anonymous Coward · 2012-10-04 22:10 · Score: 0

While I can't say for sure, this video might have just been the most pointless things I've ever streamed over the Internet.

The real representative line from TFA by Sun · 2012-10-03 16:41 · Score: 3, Informative

This wouldn't allow you to gain a "strong" piece of information – whether the cat was alive or dead – but you might be able to detect other properties.

So, in essence, the main thing they found out is how to do more stuff with qbits without triggering a collapse of the wavelength function.

Real summary:
Obscure need which is somehow quantum computing, but not in any way feline, related gets obscure advance.

Shachar

Re:The real representative line from TFA by Anonymous Coward · 2012-10-03 17:10 · Score: 0

"Next, the team measured the frequency of this oscillation. This is inherently a weaker measurement than determining whether the bit took on the value of 1 or 0 at any point, so the thought was that it might be possible to do this without forcing the qubit to choose between a 1 or a 0. However, it also introduced a complication."
So to extend the cat metaphor they measured how fast the cyclical Jesus-cat cycled between death and resurrection.... ?
Re:The real representative line from TFA by Anonymous Coward · 2012-10-03 17:16 · Score: 1

"Next, the team measured the frequency of this oscillation. This is inherently a weaker measurement than determining whether the bit took on the value of 1 or 0 at any point, so the thought was that it might be possible to do this without forcing the qubit to choose between a 1 or a 0. However, it also introduced a complication."
So to extend the cat metaphor they measured how fast the cyclical Jesus-cat cycled between death and resurrection.... ?
No, more like what colour the cat's fur is.
Re:The real representative line from TFA by hughbar · 2012-10-03 22:17 · Score: 1

If the cat is really, really dead, there will be mould on the fur [I'm assuming that the box isn't very airtight], so analysis of the reflected spectrum from the weak quantumy torch [to use the precise technical term] should pick that up.

Can I have my Nobel prize now please?

--
On y va, qui mal y pense!
Re:The real representative line from TFA by Lithdren · 2012-10-04 05:05 · Score: 1

No Nobel prize for you good sir.

The premise is that you cannot detect if the cat lives or dies from outside the box. One would deduce form this it must be, at the very least, airtight.
Re:The real representative line from TFA by hughbar · 2012-10-04 08:25 · Score: 1

Sniff! I had my hopes up. But, actually, if the box is airtight, then we can deduce [after a short while] that the cat is dead without looking or without the weak quantumy torch. Actually I wonder if the content of all these deductions are producing some effects, maybe they are information.

I think I'll go to bed now, it's been a long day at the very coalface of advanced science. I really liked that cat too.

--
On y va, qui mal y pense!
Re:The real representative line from TFA by marcosdumay · 2012-10-04 10:17 · Score: 1

That. They discovered the collor of the cat's fur, without measuring if it is dead or alife. Thus, the cat is still 1/sqrt(2)*(dead; alife), but it is definitively black.
And quantum mechanics go on well alife, despite TFS calling it dead.

--
Rethinking email

Quantum cryptography? by timeOday · 2012-10-03 16:41 · Score: 4, Interesting

What? Isn't the proven destructiveness of measuring a quantum system the bedrock of quantum key distribution?

Re:Quantum cryptography? by mcrbids · 2012-10-03 16:49 · Score: 1

Came here to see this point made, was not disappoint.

--
I have no problem with your religion until you decide it's reason to deprive others of the truth.
Re:Quantum cryptography? by Anonymous Coward · 2012-10-03 16:55 · Score: 0

I didn't read TFA, but schrodinger's cat was about large objects being able to go in superposition. So maybe they were able to peek at a large object which is and stays in super position.
The bits (single photons) being send in quantum key distribution are not in superposition, since the sender knows which random bits are send.
Of course I could be very wrong, I am not a quantum scientist.
Re:Quantum cryptography? by Black+Parrot · 2012-10-03 17:12 · Score: 1

What? Isn't the proven destructiveness of measuring a quantum system the bedrock of quantum key distribution?
I thought I remembered a recent story saying that researchers had found a method to "peek" at an quantum-encoded message without tipping Bob and Alice off to the fact that they had an eavesdropper. I wonder if this story is related to that.

--
Sheesh, evil *and* a jerk. -- Jade
Re:Quantum cryptography? by Yvanhoe · 2012-10-03 17:30 · Score: 3, Informative

I thought at this point is had become obvious that quantum cryptography was just a nice scam to fund fundamental physics research?

--
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
Re:Quantum cryptography? by Anonymous Coward · 2012-10-03 18:41 · Score: 0

IIRC there have been 2 methods that 'break' quantum encryption so far.
1: The data is fully intercepted, determined and a copy is sent further along. Of course this requires access to the system, which is rather difficult.
2: Data is read, but only up to a certain %. Quantum computing is inherently unstable and a certain % of the data can be wrong (i think 5-10% depending on the system). This method won't give you all the data, but you could make an educated guess.
Re:Quantum cryptography? by DontLickJesus · 2012-10-03 19:35 · Score: 1

No information is gathered, rather the lifetime / distance of the qubit is extended. Since this caused the frequency of detection to change, I'm going to make an educated guess that the correction signal causes interference and/or destruction of a third channel which could be monitored for manipulation.

--
Where genius and insanity become confused true wisdom is found
Re:Quantum cryptography? by Artifakt · 2012-10-03 19:51 · Score: 1

If an object the mass of a cat and composed of normal matter can exist as a quantum superposition, then mass and particle complexity are not fundamental limits. If the cat is possible, the Planet Jupiter can also exist in a Schrodinger's Cat like state.
Then there's the question of what constitutes an observer. Mystical models assume something that is itself aware. The extreme antropomrphic end of observer definitions is "a being capable of understanding the implcations of Quantum Mechanics with regard to the given wave function". That interpretation means lots of humans don't qualify as observers. From there, the definitions tend to stay mystical, with debate over whether a being that can notice a light change from off to on, but has no idea what it implies, counts as an observer. One potential definition goes into whether the cat itself is aware, and whether that includes the cat having a related but possibly different thing we call "self awareness", and so on. The less mystical models treat any instrumentation capable of providing data as an observer, or even anything that can be toggled to a different logic state by interacting with the collapse of a particular state vector. By that sort of definition, an 'observer' is therefore any 'material' thing that is outside the array of matter that is part of your initial state vector, but only at the moment that outside object recieves data on the state vector.
So, if the initial superposed object is the planet Jupiter as it exists at time T, then a liberal definition of observer means that state vector collapses a tiny fraction of a jiffy later when it reacts with the first particle we are not defining as part of Jupiter. On the other hand, limiting observers to beings with human-like awareness means that we can say only that Jupiter was a planet an hour or so ago, when the light we just recieved left it, but Jupiter is an 1 hour duration (approximately) state vector. That's one of the things that tends to make a mystical interpretation of "Observer" seem nonsensical when it's baldly stated like that.
However, consider General Relativity. Relativity tells us using "is" and "was" to describe something at the other end of a beam of light isn't really meaningful, particularly across increasing distances. Simultanity is what the word 'is' implies, and that concept's really breaking down even if we don't go into Jupiter as a quantum state vector but stick with good old Einstein and say Jupiter is a planet at the other end of a one hour light cone from us but it becomes absurd to say "That was an hour ago, what is Jupiter doing simultaniously with now here on Earth?".
Should we reject the mystical definition of an observer then? Even if it sounds weird or like some sort of religious philosophy contaminating the purely scientific explanation, in some ways it's really just forcing us to a similar position as Relativity does anyway.

--
Who is John Cabal?
Re:Quantum cryptography? by L4t3r4lu5 · 2012-10-03 20:04 · Score: 1

I thought at this point is had become obvious that quantum cryptography was just a nice scam to fund fundamental physics research?
We shouldn't need to scam anyone to fund fundamental physics research.

--
Finally had enough. Come see us over at https://soylentnews.org/
Re:Quantum cryptography? by Yvanhoe · 2012-10-04 01:19 · Score: 1

I totally agree, we should need. But we do need.

--
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
Re:Quantum cryptography? by Anonymous Coward · 2012-10-04 03:35 · Score: 0

Citizen! Why are you not using your hack-proof quantum key the government has provided you? Don't ask how we know.

Bazinga by selectiontimeout · 2012-10-03 16:41 · Score: 1, Funny

You're welcome.

Entanglement? by Anonymous Coward · 2012-10-03 16:49 · Score: 0

Could this be used to make communication via entanglement viable?

The cat is dead by mveloso · 2012-10-03 16:52 · Score: 1

If the cat isn't dead now, it will be eventually. So you might as well assume it's dead and move on.

Re:The cat is dead by toriver · 2012-10-04 05:33 · Score: 1

Ah, are we getting some economics into our physics now?
"In the long run, we are all dead" - John Maynard Keynes.

We have to name it... by irving47 · 2012-10-03 16:59 · Score: 5, Funny

Can we PLEASE call it a Heisenberg Compensator?

--
I had a sucky sig.

Re:We have to name it... by Anonymous Coward · 2012-10-03 17:38 · Score: 0

Second!
Re:We have to name it... by Tempest451 · 2012-10-04 01:39 · Score: 1

I third this!
Re:We have to name it... by Tempest451 · 2012-10-04 01:39 · Score: 1

Funny that Star Trek thought this was possible long before the actual experiments.

whodathunkit? by Tumbleweed · 2012-10-03 17:01 · Score: 2

Stargate SG-1 finally got some science right!

Re:whodathunkit? by Tempest451 · 2012-10-04 01:41 · Score: 1

Actually Star Trek beat them to the punch with the Heisenberg Compensator.
Re:whodathunkit? by Anonymous Coward · 2012-10-04 05:33 · Score: 0

No one likes a jealous person

every time ... by SchroedingersCat · 2012-10-03 17:06 · Score: 5, Funny

Every time they take a peek, God kills a kitten.

Re:every time ... by TheInternetGuy · 2012-10-03 17:34 · Score: 2

Every time they take a peek, God kills a kitten.
Only if the kitten is entangled with the cat in the box.

--
If my comment didn't sound as good in your head as it did in mine, then I guess we all know who's to blame
Re:every time ... by Mashdar · 2012-10-04 03:09 · Score: 1

He entangles us all in His noodley appendages.

Looks like Schrodingers Cat stayed alive by toygeek · 2012-10-03 17:11 · Score: 1, Offtopic

just long enough to be eaten by Pavlov's Dog

--
Nobodies Prefect
Tidbits for Techs Technology Blog

Entangled Garments by Penurious+Penguin · 2012-10-03 17:21 · Score: 3, Funny

Rather than using small fury creatures with no propensity for entangled behavior, why not use something of similar size, but a bit more gracious and flat? For this I propose the noble sock - an item exhibiting (when in certain steel chambers) extremely random tendencies of existence and non-existence. We all know damned well what to expect of a cat run through a permanent-press cycle. However, no one, not even Martha Stewart knows what to expect of the sock - that ambiguous textile for which any state even science cannot predict.

--
Forward! -- Emperor Norton, 2012

Re:Entangled Garments by DMUTPeregrine · 2012-10-03 20:08 · Score: 1

Naw, it's actually easy. The spinning motion of the drier cycle forms a wormhole, and when the socks are transported through it they end up in closets, transformed into coat hangars.
Go, look in your closet. Did you buy all those hangars? No! Most of them used to be your socks.

--
Not a sentence!
Re:Entangled Garments by hweimer · 2012-10-03 21:00 · Score: 1

Two words: Bertlmann's socks.

--
OS Reviews: Free and Open Source Software
Re:Entangled Garments by steelfood · 2012-10-04 04:53 · Score: 1

It works out when you take into consideration socks come in pairs. CP violation states that you will get back a full pair most of the time, but occasionally, you will only get one.

--
"If a nation expects to be ignorant and free in a state of civilization, it expects what never was and never will be."
Re:Entangled Garments by camperdave · 2012-10-04 05:36 · Score: 1

Once one of my socks changed state from right hand...er footed to left footed. I was unable to wear that pair anymore because, at best, I would wind up walking in circles; at worst, I would stumble and fall. I have been unable to reverse the effect.

--
When our name is on the back of your car, we're behind you all the way!

Copenhagen Interpretation by dryo · 2012-10-03 17:26 · Score: 2

More chinks in the armor of the abominable Copenhagen Interpretation. Bohr, Heisenberg and Schreodinger were very smart people, but they couldn't be right about consciousness affecting physics. That's just stupid.

Re:Copenhagen Interpretation by Anonymous Coward · 2012-10-03 18:05 · Score: 1

they couldn't be right about consciousness affecting physics.

Why not? Seems like you'd need to provide pretty strong evidence for that claim. Before you waste everyone's time with more ridiculous bullshit, you can't.
Science doesn't exist to conform to your poorly-informed world view.
Now, stop fellating your play-pretend scientist buddies and go read a book. You know, learn something before you spew idiotic nonsense like this around the internet.
Re:Copenhagen Interpretation by Anonymous Coward · 2012-10-03 20:08 · Score: 0

You stupid asshole, _you_ need to provide the evidence. Consciousness affecting physics is laughably improbable, and exceptional claims require exceptional proof.
Re:Copenhagen Interpretation by expatriot · 2012-10-03 21:55 · Score: 3, Insightful

1. Stop being a jerk
2. Look up the work on collapse of interference in the double slit experiment.
3. If you can determine conclusively what constitutes an observation of a quantum system, you will be in line for a big prize.
4. Ignore any discussion of cats. It is a joke that everyone has fallen for.
Re:Copenhagen Interpretation by Anonymous Coward · 2012-10-04 04:53 · Score: 0

Posting as AC because accounts are for egoists:
If the state of A has any effect on the state of B, B observes A. There is no limit to the simplicity of entities A and B so long as any of their properties (quantum state, space-time coordinates) are dependent on each other's properties. However, in an isolated system consisting of only A and B, no observation can occur because the effects on A and B's properties are recursively interdependent. In python:
def observe( self, other ):
self.state = self.state != other.state
other.observe( self )
Add in entity C with properties mutable in a way dependent on the properties of A, B, or both, and everything changes.

New Scientist? by edibobb · 2012-10-03 17:34 · Score: 4, Informative

The New Scientist frequently makes quantum leaps in logic. Or was that logic leaps in quantum physics? I GET SO CONFUSED! At any rate, the real article is a bit less sensational.

http://www.nature.com/nature/journal/v490/n7418/full/nature11505.html

Re:New Scientist? by Tempest451 · 2012-10-04 01:43 · Score: 0

Same information just more calculations.

Observing, Not Avoiding by jIyajbe · 2012-10-03 17:58 · Score: 4, Interesting

From the abstract:

"The act of measurement bridges the quantum and classical worlds by projecting a superposition of possible states into a single (probabilistic) outcome. The timescale of this 'instantaneous'process can be stretched using weak measurements usuch that it takes the form of a gradual random walk towards a final state. Remarkably, the interim measurement record is sufficient to continuously track and steer the quantum state using feedback..."

The way I read this, they aren't claiming they prevented collapse, nor that they can predict which state it will collapse to; rather, they have (1) increased the time of the collapse of the wave function (via feedback) and (2) been able to "watch" the electron collapse to whichever state it goes to. [N.B.: I am totally open to correction. I haven't paid the $32 for a copy of the paper.]

So, no Heisenberg compensator here.

--
"Don't blame the log for the fire." --Andrew Ratshin

Re:Observing, Not Avoiding by Zaphod+The+42nd · 2012-10-04 02:15 · Score: 1

This is my interpretation, people are blowing this out of proportion for sensationalist news (bad newscientist!)

That said, IANA Physicist

--
GCS/MU/P d- s:- a-- C++++$ UL++ P+ L++ E+ W++ N o K- w--- O M+ V- PS+++ PE Y+ PGP t+ 5- X R++ tv+ b++ DI++ D++ G+ e++ h-
Re:Observing, Not Avoiding by sgt_doom · 2012-10-04 06:00 · Score: 1

You know, most people still don't understand Bell's Theorem and believe in that EPR paradoxy.

Unfortunately... by srussia · 2012-10-03 18:01 · Score: 1

the p -value of their "weak measurements" was 0.5

--
Set your phasers on "funky"!

Actually it is right but also wrong by aepervius · 2012-10-03 18:39 · Score: 1

The point of the cat thought experiment was to show the absurdity of taking QM at macro level.

--
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org

'quantum' as a marketing buzzword_and 'no' by globaljustin · 2012-10-03 18:40 · Score: 1

Excellent question...I have thought much about it, as it used to be my job. Two electrons entangled in a true quantum state would be a perfect communication device...any change to the state of one would instantly change the other in the same way regardless of distance

In that **truly quantum** scenario, we would indeed have quantum signal transmission at a rate of 1/1...faster than the speed of light...instant over any distance...

That's **kind of** a big deal...Einstein called it "Spooky Action at a Distance"...it's definitely theoretically possible...and it definitely would turn particle physics on its head...and it most likely won't happen b/c the energy required to do it is probably equal to all the energy in the universe according to known science. (if you balance out the equations)

That's why I cringe every time I see 'quantum' used in reference to computing...its just marketing terms for a faster processor at this point

--
Thank you Dave Raggett

Re:'quantum' as a marketing buzzword_and 'no' by RightSaidFred99 · 2012-10-03 20:04 · Score: 2

Two electrons entangled in a true quantum state would be a perfect communication device...any change to the state of one would instantly change the other in the same way regardless of distance
That's mumbo jumbo and simply untrue. Both have a state, peeking at one just tells you what the other is it doesn't change any state.
Quantum "instant" communication is impossible and will therefore never happen.
Re:'quantum' as a marketing buzzword_and 'no' by Anonymous Coward · 2012-10-04 03:29 · Score: 0

As someone who has to also think about it a lot, as my current job is physics research... no, even in the ideal quantum cases, no know faster than light communication schemes exist, and mathematically, entanglement schemes can be shown to not allow such communication. No, not anything you do to one half will change the other half though, as many actions will just destroy the entanglement instead. And no, it has nothing to do with energy requirements, as it is not like there is some energy threshold that open up new options within those theories. Yes, actions on one half of an entangled pair can affect the state of the other half, but they cannot change the probability distribution of measurements for the other half. In the stereotypical example using entangled spins, regardless of which ever end measures first or does something to the spin, both sides end up with 50-50 measurements of up and down states.
And quantum computing is not about making a faster processor, at least in the general purpose sense. It has been about performing specific algorithms (from a very short list...) with a different complexity class than thought possible with classical computers. Maybe new, more generally useful algorithms will be found, but in the mean time it is like early graphics processor development, except intended for an even narrower set of possible applications.

Re:Next up Photons Smotons by globaljustin · 2012-10-03 18:46 · Score: 0

Interesting...IMHO what we call a 'photon' is essentially a different flavor of Higgs-Boson, not any sort of 'light packet' or somesuch...same for the 'graviton'...they are all just variations on the same thing...a thing that is **not** gravity

Essentially I'm saying maybe this means there are only two forces, strong/weak/electro/mag and gravity...

--
Thank you Dave Raggett

Re:first post ! by Cryacin · 2012-10-03 18:53 · Score: 4, Funny

Does anyone here RTFA?

Of course! It's about scientists no longer using sledgehammers to check for the existence of cats in a box. Instead they shine a torch inside. Quite obvious really!

--
Science advances one funeral at a time- Max Planck

Obligatory Portal reference by Anonymous Coward · 2012-10-03 18:58 · Score: 0

The cat is alive.

Does this imply FTL comms? by pipedwho · 2012-10-03 19:11 · Score: 1

If the state of an entangled set of quantum bits can be known in advance and their states observed without collapsing them, then it stands to reason that a remote communications station with a pre-delivered set of pre-entangled bits could receive a message by observing the collapse the instant the 'transmitter' causes it to happen.

I wonder if this research provides this possibility, or if there is something inherent to the entanglement/observation process that prevents this.

Re:Does this imply FTL comms? by Zaphod+The+42nd · 2012-10-04 02:21 · Score: 1

Oh gosh no. First, this does not mean that quantum bits state can be known "in advance" (whatever that means, if you detect the state before collapse, does that mean they could later collapse into a different state? If so, that's pointless. If not, then its already collapsed). The way I read the article, it doesn't mean they can observe state without collapsing, but rather can gain some information about it before collapsing by effectively stretching out the collapse into a series of gradual collapses about different axis, collapsing different parts and gaining information about them as you go. So that doesn't follow. Furthermore, even if you COULD observe a quantum entanglement without collapsing it, how does that help you with remote communications? Merely transmitting quantum information doesn't enable you to communicate in any meaningful way other than random data. You simply cannot transmit classical information (a message) via quantum information. Lets say two qubits are entangled, you still have to send one of those qubits to the other person at sub-c, so what good is having entangled qubits at that point? There's no way to entangle two qubits, send one to someone, and then control the collapse, which is what would be necessary for FTL comms. Even if you could observe it, that isn't good enough. Sorry, as cool as FTL comms are.

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GCS/MU/P d- s:- a-- C++++$ UL++ P+ L++ E+ W++ N o K- w--- O M+ V- PS+++ PE Y+ PGP t+ 5- X R++ tv+ b++ DI++ D++ G+ e++ h-
Re:Does this imply FTL comms? by leonardluen · 2012-10-04 02:50 · Score: 1

i believe the problem is that it might be possible to know what it will collapse into, but we still can't influence how it will collapse.
so the receiver will know it will likely collapse into state X before actually measuring it...how does that really help anything? you are just sort of measuring it earlier.

I very gently opened the link by niftymitch · 2012-10-03 19:12 · Score: 1

I very gently opened the link and found that
it kept changing. At best it seems to be a
suggestion that perhaps maybe the cat has
whiskers that wiggle. As long as I look gently
on a windy day the whiskers could be wiggling because
it was alive or the wind was blowing.

Even the Google ads kept changing.
I think Google could be a cat killer if the
quantum bits was a Google search engine.

--
Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities; Truth isn't. Mark Twain.

Re:I very gently opened the link by toriver · 2012-10-04 05:45 · Score: 1

Maybe link shorteners and QR code URLs are the new cats? You do not know what the link will lead to until you click it, thus collapsing the waveform of the web...

Re:first post ! by Anonymous Coward · 2012-10-03 19:20 · Score: 5, Informative

Does anyone here RTFA?

Yes, I did. The summary quotes this part line by line: "physicists have managed to probe a delicate quantum state without destroying it – the equivalent of taking a peek at Schrodinger's metaphorical cat without killing it."

This shows a fundamental misunderstanding of the cat experiment, in that the author is assuming that by opening the box the cat gets killed. When in fact the cat can be considered both alive AND dead while the box is unopened, and if you open it it might very well be alive and not dead. Thus it would be equally accurate (or inaccurate, rather) to say "the equivalent of taking a peek at Schrodinger's metaphorical cat without making it LIVE."

And to be even more nitpicky, it does alter the quantum state- it changes the oscillation but does not destroy the superposition. They also have (simply put) found a way to return the oscillation to the pre-observation state within a relatively small timeframe.
So yes, the parent's "???" was justified as the use of the analogy was horrible incorrect.

The Air in the box observes the Cat. by Anonymous Coward · 2012-10-03 19:30 · Score: 0

The Air observes the Cat, the Box observes the Air, The human observes the Box -- Before the experiment the Universe is observing all the components: Before, during, and after the experiment the waveform is collapsed. The cat was only ever both alive and dead in some imaginary incomplete explanation of a property that our incomplete quantum theory has.

Headline? by wonkey_monkey · 2012-10-03 19:50 · Score: 2

Quantum Measurements Leave Schrödinger's Cat Alive

Shouldn't that be "Quantum Measurements Leave Schrödinger's Cat In A Superposition Of Alive And Dead"? If it's decidedly alive then the waveform has collapsed, and isn't that what they're avoiding? (did not read TFA)

--
systemd is Roko's Basilisk.

But then curiosity killed the cat anyway? by Anonymous Coward · 2012-10-03 20:28 · Score: 0

But then curiosity killed the cat anyway?

Who cares? by sconest · 2012-10-03 20:29 · Score: 1

Schrödinger's cat has surely died of old age by now.

--
Guvf vf abg n EBG zrffntr

Re:first post ! by Savage-Rabbit · 2012-10-03 20:42 · Score: 4, Interesting

This shows a fundamental misunderstanding of the cat experiment, in that the author is assuming that by opening the box the cat gets killed. When in fact the cat can be considered both alive AND dead while the box is unopened, and if you open it it might very well be alive and not dead. Thus it would be equally accurate (or inaccurate, rather) to say "the equivalent of taking a peek at Schrodinger's metaphorical cat without making it LIVE.

I'm not a quantum physicist but If I understand Schrödinger's experiment correctly (feel free to reeducate me), the cat is both alive and dead until you open the box and 'fix' it's state. Until you observe the cat all you can say is that the closer you get to an hour (the radioctive matierial decays one atom per hour) the more likely it is that the cat is dead. So have these scientists managed to observe Schrödinger's cat in it's dual live/dead 'flux' state?

--
Only to idiots, are orders laws.
-- Henning von Tresckow

Look it up & get back w/ me by globaljustin · 2012-10-03 20:52 · Score: 2

No, you're just wrong...and you actually agreed with me when you said, "...will never happen."

See, you really need to read up on 'Action at a Distance' because it is *exactly* the phenomenon you, I, and particle physics thinks will not and cannot happen...

Yet, Einstein himself identified it as predicted in his models....seriously look it up

--
Thank you Dave Raggett

Re:Look it up & get back w/ me by Anonymous Coward · 2012-10-04 01:45 · Score: 0

What about the no-communication theorem?

I saved Schrödinger's Cats life by Anonymous Coward · 2012-10-03 20:54 · Score: 0

I managed to save Schrödinger's Cat. How so? This is what I did:
a. The cat is an observer - i.e., it can smell whether or not a toxic gas is being released.
b. The cat is a constant observer - cats are known for sleeping in brief periods of time called "cat naps".
c. The cat is a constant observer that triggers the Quantum Zeno effect [Wikipedia: https://en.wikipedia.org/wiki/Quantum_Zeno_effect] - thus postponing indefinitely the unstable particles decay.
Of course it is assumed (as it was on the original experiment) that the cat never starves or asphyxiates.-Ignacio Agulló

Point is moot by BananaBender · 2012-10-03 21:18 · Score: 1

According to Quantum_decoherence, there is no superposition of quantum states. As the radioactive element interacts with the cat and the box, its decoherence time becomes very short, so the wave function collapses almost instantly. The cat is either dead or alive, but there is no extended state of superposition.

Schrödinger's Cat is Lame anyway you look at by Anonymous Coward · 2012-10-03 22:01 · Score: 0

For a real Schrödinger's Cat you need to superimpose a dead and a living cat. Furthermore the dead cat needs to be the deceased remains of the living cat. This would imply a violation of the principle of causality.

Knowledge itself does not lock the quantum state? by adam.skinner · 2012-10-03 22:04 · Score: 1

Looks like knowledge of the quantum state does not lock it in place, then.

(5, Hilarious) by Anonymous Coward · 2012-10-03 22:12 · Score: 0

So, in other words, instead of poking the cat to see if it's alive, we've been hitting it with a sledgehammer.

Re:first post ! by TheDarAve · 2012-10-03 22:18 · Score: 2, Funny

So have these scientists managed to observe Schrödinger's cat in it's dual live/dead 'flux' state?

They must work for the Umbrella Corporation.

Quantum cryptography implications by the+cleaner · 2012-10-03 22:26 · Score: 1

Someone enlighten me: Have we just cracked quantum cryptography?

--
Could be worse. Could be raining.

Re:Quantum cryptography implications by rtfa-troll · 2012-10-10 22:31 · Score: 1

As I understand it:
No in theory. However, in real life most quantum crypto systems don't 100% match the theory so this is yet another hint that they have to be designed much more carefully than many people initially thought. For example, the typical analysis of a quantum crypto system assumes that one single photon is sent at time. In real systems that is sometimes true and sometimes not (two come out at the same time e.g.). If you measure carefully enough you may be able to pick a small proportion of the spare photons and learn something about the traffic. Probably this will give some hints to someone about how to measure some practical quantum crypto systems.
So; theoretical quantum cryptography is not broken. Practical quantum crypto is already broken. If you are investing in such a system, then ensure that you are using the strongest available standard crypto and the most carefully designed operational procedures as well as using quantum crypto. Otherwise you are spending money in the wrong place.

--
=~ s,(.*),<sarcasm>$1</sarcasm>,g if any_point_you_wish();

This is interesting, but the title is misleading. by jsternbe · 2012-10-03 22:54 · Score: 3, Insightful

The headline was a bit misleading. You still can't measure a quantum state without having its superposition collapse to what was measured. If I understand what the article is saying properly, these scientists are not able to peak into the box to measure "Schrodinger's Cat's" state of aliveness, but they can still peak to see if the cat is a tabby or a calico. If fur pattern isn't a good quantum number, then that will cause the "cat" to change its spots, but later probes can be used to nudge it back to its original state. Meanwhile, you haven't disturbed the "cat's" aliveness or deadness. The important part seems to be being able to "nudge" certain states with probes to get some information out of the system without really changing it.

Re:first post ! by Anonymous Coward · 2012-10-03 22:55 · Score: 4, Interesting

The Schrödinger's cat is just great marketing for a very straightforward statement. The cat is alive (cat = 1) in 50% of the worlds, the cat is dead (cat = 0) in 50% of the worlds, but you don't know in which world you are until you look at the cat (a.k.a. "collapsing the space of probabilities", big marketing words for a straightforward concept). Schrödinger's merely says that the cat's expected value is: 0.5 * 1 + 0.5 * 0 = 0.5 (but this is a statistics mean, doesn't imply that the cat is both alive and death, just like families never have 1 kid and a half)

The correct way to say it, is that schrödinger's cat is a projection in 3D space of a 4D space problem, where the 4th dimension is the set of "alternate scenarios", and the cat's value at a certain position, is its expected value in that position (a "fuzzy variable").

While you can't get worthwhile info from studying a single cat system without "opening the box", you can discover a lot from a system with many cats; for examples, take a look at nonograms.

"One atom per hour" by Kupfernigk · 2012-10-03 22:55 · Score: 3, Informative

No, that too is incorrect. Radioactive decay is random. With a very slow rate of decay ( averaging one event per hour) the time between events will, I think, follow a Poisson distribution. The probability that the cat is dead does indeed increase with time, but it is not 1 at 1 hour, or even 2.

My dog suggests that this should be tested with a very large number of cats, and a big lump of polonium in each box.

--
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."

Re:"One atom per hour" by Bengie · 2012-10-04 00:19 · Score: 1

Radioactive decay: http://science.slashdot.org/story/12/09/01/1731224/radioactive-decay-apparently-influenced-by-the-sun
Not entirely random
Re:"One atom per hour" by MobyDisk · 2012-10-04 02:01 · Score: 1

You misunderstand: the statement "Radioactive decay is random" means that "the time between each individual decay event is random." It does not mean "there are no factors that can influence the overall rate of decay."

But we do...politicians by Kupfernigk · 2012-10-03 23:04 · Score: 2

Until the Manhattan project politicians didn't see the need for fundamental physics research. (Winston Churchill being a notable exception). As the nuclear industry becomes, basically, about as exciting as the coal mining industry, the perception of the need recedes. We are back to trying to invent military uses for pure research. But if the monkeys hold the keys to the banana plantation, I think we are justified in pulling wool over the eyes of the monkeys.

--
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."

Re:BOO BEAR of peeking without killing it ?! by Anonymous Coward · 2012-10-03 23:35 · Score: 2, Funny

""The probability distribution does not apply to a single cat, but rather to an ensemble of cats. Repeat the experiment 1000 times and you'll get about 500 alive and 500 dead.""

The whole point of these experiments is to front the whimsical idea of someone, somewhere performing them 1000 times. "What did you do today, honey?" "Number 782." "Alive or dead?" "I'd rather not discuss it." "Oh really--does that mean this cat is in an undetermined state?" "Yeah--for you, now shut up and pass the peas."

Or you go to your doctor and she says, you have a 50 per cent chance of survival for the coming year. Oh shucks, you say, does this mean I'm going to have to crawl into a stupid box and wait? Who is going to open the box? What if no one opens the box? What if someone buries the box? Does this mean that in the last minute I am slightly more statistically dead already? Can I pay you in a year? "I rather you paid now." Oh, that means zero chance for survival.

According to statistics, one 30-millionth of 'you' will perish in a commercial airline accident over the course of your lifetime. Just a few cells here and there, yet something to brush off lightly.

If you've had a brush with death, do not use it on your cat.

95% of lawyers give the other 5% a bad name.

A casino is the box experiment in our reality. So long as you have money are playing you could yet still be someone and not some compulsive irresponsible bum. Here sir, have an hors'd'oeuvre. Take this chit to the bar for a free undetermined-state drink. As the evening wears on and your money is gone and you're just roaming the aisles trying to look like you lost something and the men in suits are following you discreetly and whispering into their armpits, the world outside can only observe you in an undetermined state. Then the box opens itself and you are chucked out and the experiment concludes.

50% of this message is bullshit. The other half is hors'd'hooey.

Schrodinger's Cat by Benchevy · 2012-10-03 23:55 · Score: 2

I believe that the idea is that by peeking, they can see one reality, but, since they didn't technically cause one reality to collapse, they can peek again and then the outcome has a 50% chance to have a different outcome.

Re:first post ! by cyber-vandal · 2012-10-04 00:08 · Score: 4, Funny

The cat can be in three states: alive, dead and bloody furious.

Yep, completely rewritten! by korielgraculus · 2012-10-04 00:32 · Score: 2

We only managed a quick peek, but the cat is definitely dead. Or asleep. We think.

Right... by Impy+the+Impiuos+Imp · 2012-10-04 00:33 · Score: 1

> the equivalent of taking a peek at Schrodinger's metaphorical cat without killing it.

I'll believe it when I see it.

Oh, wait.

--
(-1: Post disagrees with my already-settled worldview) is not a valid mod option.

one question remains by Anonymous Coward · 2012-10-04 00:51 · Score: 0

Very informative comments so far. I just have one question. Is the cat dead or alive? I'm out of cat food and need to know if I should buy more.

I don't get it... by Anonymous Coward · 2012-10-04 00:52 · Score: 0

I don't get it. Why not just shoot the damn cat?

Re:I don't get it... by leonardluen · 2012-10-04 02:56 · Score: 1

because then you wouldn't get zombie cats.

Re:first post ! by drainbramage · 2012-10-04 01:15 · Score: 1

So it is more like they are checking the cat's box tor signs that the cat is still alive?

--
No brain, no pain.

Isn't that cat dead yet? by Anonymous Coward · 2012-10-04 01:19 · Score: 0

It must of died of old age by now.

But.. by Anonymous Coward · 2012-10-04 01:25 · Score: 0

..this article may just have killed it!

If you're leaveing it alive ... by damn_registrars · 2012-10-04 01:55 · Score: 1

... isn't that determining the state? The purpose of the cat experiment was to state that it is both alive and dead until observed to be one or the other.

And for that matter, opening the box does not kill the cat, it just allows you to observe its state. We know that when you open the box there is a set probability of the cat being dead.

--
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.

Re:first post ! by tom17 · 2012-10-04 02:06 · Score: 2

Your scenario presumes the cat is alive *or* dead.

I thought this too for a long time, it's only since I recently started reading more on quantum mechanics and the truly baffling experiments that have been done, that I started to understand (or is that, started to confuse) more. In fact, the metaphorical cat is both dead and alive at the same time. It is not in an unknow-but-determined state already. Observing it does not show that it was already dead or already alive. Observing it makes it fall into one of those states.

"But that makes no sense"

Yep, and it's still hurting my head too...

Of course, this might change all that...

ITT Quantum Misconceptions by Zaphod+The+42nd · 2012-10-04 02:14 · Score: 1

Jeeze, I'm really starting to think that most people just shouldn't ever talk about Quantum, there's so many misconceptions and misunderstandings that trying to give people a little bit of information, since its so wildly out of context, even in the wrong context (misconceptions), that it only drives them further away from the truth, from reality. People latch onto the wrong points.

I barely understand Quantum Physics myself and I can tell that TFA makes all kinds of wild leaps in logic. Most of these things aren't true, and the way they explain the Schrodinger's Cat experiment makes the classic misunderstandings.

The reality is far less sensational: http://www.nature.com/nature/journal/v490/n7418/full/nature11505.html

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GCS/MU/P d- s:- a-- C++++$ UL++ P+ L++ E+ W++ N o K- w--- O M+ V- PS+++ PE Y+ PGP t+ 5- X R++ tv+ b++ DI++ D++ G+ e++ h-

Re:first post ! by Will.Woodhull · 2012-10-04 02:41 · Score: 1

The true state of the cat is that it is not dead yet.

It is not alive in any functional way since like a good cubicle minion it is not interacting with anything outside of its box. And sooner or later it will be dead, for that is the eventual fate of all cats and minions. But since it is possible that the box may be opened somehow before the inevitable death, even though it is not functionally living at the moment we cannot say it is truly dead yet.

There is an equivalent situation in USA Presidential politics right now. At this moment whether Obama or Romney wins the election depends on whether a small number of undecided registered voters come out of their 'don't give a damn' boxen and participate one way or the other. An interesting thing is that this small number of Schrödinger's voters are influencing millions of dollars of campaign expenses. Enough to fund the teacher's salaries for a small city for several years. Enough to pay for the implementation of meaningful election reform on a nationwide basis. Enough to pay the salaries and perks that the USA Congress critters have given themselves for a day or two. Truly a great deal of money.

The implications for quantum engineering are great, but unfortunately this slashdot comment is not large enough to contain the explanation.

--
Will

Re:first post ! by leonardluen · 2012-10-04 03:04 · Score: 1

it is more like they are measuring the color of the cat's fur, but don't know if it is alive or dead.

and there seems to be a another consequence of this experiment, if the superposition state is collapsing, they are able to nudge it back into a superposition.

Re:first post ! by Nethemas+the+Great · 2012-10-04 03:09 · Score: 1

I think it makes sense. You have something oscillating between states 0 and 1 like a teeter totter with evenly weighted people on either side. The act of measuring the state is like introducing a weighted ball to the fulcrum point. Which ever side of the teeter totter is closest to the ground will have the weighted ball roll towards it thus fixing the teeter totter in that state.

--
Two of my imaginary friends reproduced once ... with negative results.

Heisenburg Compensator by Anonymous Coward · 2012-10-04 03:12 · Score: 0

Captain Picard: "Geordi, how does the Heisenburg Compensator on the transporters work?"
Geordi: "Quite well, sir!"

Re:Heisenburg Compensator by Electricity+Likes+Me · 2012-10-04 05:02 · Score: 1

That was always the biggest piece of unnecessary technobabble. There's nothing "quantum" about the demands of the reassembling ordinary matter.

Shroedinger's cat is not alive or dead by Alien7 · 2012-10-04 03:22 · Score: 1

but we are certain it has fleas!

Thread Over by Anonymous Coward · 2012-10-04 03:38 · Score: 0

RightSaidFred chose his words carelessly. You are all correct but talking about different things.

Yes, there is "communication" in the sense of "spooky action at a distance". No, you cannot transmit classical information that way.

Re:Thread Over by Electricity+Likes+Me · 2012-10-04 04:57 · Score: 1

RightSaidFred chose his words carelessly. You are all correct but talking about different things.
Yes, there is "communication" in the sense of "spooky action at a distance". No, you cannot transmit classical information that way.
Except what we do know is that currently you're simply forbidden from transmitting information faster then light this way. There's nothing that would forbid "spooky action at a distance" from transmitting information at or below light speed, provided some means could be found to allow it to do that.
This would still be a huge discovery in a world where electromagnetic spectrum is highly limited and interceptible, and it's why I find these weak measurement experiments so interesting. You could imagine for example, that you have a big collection of spin-entangled electrons in a device, that you push around weakly, and then transmit a synchronization signal at light speed to indicate to a receiver that it's safe to read off the state of their entangled electrons. You wouldn't be able to talk faster then light, but you'd have wireless communications with effectively infinite bandwidth.
Re:Thread Over by Anonymous Coward · 2012-10-04 09:01 · Score: 0

Usually the limits for communication via entangled states say nothing about the actual speed of communication. In other words, they don't allow the quantum channels by themselves to communicate at any speed. In order for them to be used for communication you need a classical communication channel, which goes back to needing some sort of wireless, fiber, cable, etc., connection still. Also doesn't help that currently foreseeable practical limits would require a fiber or other optical signal to entangle particles in the first place, although that might be over come later.

Mod parent up by Anonymous Coward · 2012-10-04 04:11 · Score: 0

Math is a human description of the world, only the pythagoreans and their modern day equivalents think that the world is somehow made of mathematics. There is a lot of junk math generated to create theories for how the world works, but unless it accords with other non "mathematical" descriptions of a the given event it is trying to describe it isn't useful.

Newtonian physics aren't very useful in modeling the double slit experiment as they will generate an incorrect answer! However, using string theory instead of Newtonian physics to simulate two balls with different masses falling through space is a *really* stupid idea. Indeed, with todays computing power one wouldn't be able to finish the simulation ... making a string theory as useless as using newtonian physics to describe the double slit experiment.

Re:first post ! by Electricity+Likes+Me · 2012-10-04 04:46 · Score: 1

That misses the point too though.

The original point of the Schrodinger's cat thought experiment was to highlight an absurdity of quantum mechanics: that if we chained enough causality to a quantum state, the mathematics showed that we ended up with conclusions like a living organism being both alive and dead at the same time (and then as time goes on, both alive and hungry, and dead and decaying, at the same time).

The obvious problem of this becomes more apparent when you consider the proposition that the cat has agency, or could be a physicist instead. If the experiment is collapsed by observation, what is observation, given as if we also locked a physicist in the box with the cat he too would be alive and dead at the same time.

Re:first post ! by OakDragon · 2012-10-04 04:53 · Score: 4, Funny

Is that a British torch or an American torch? The cat's fate may yet be undecided!

--
Dark Reflection

Re:first post ! by OakDragon · 2012-10-04 04:54 · Score: 1

And if you wait for, say, three weeks until you open the box, the cat will almost definitely be dead.

--
Dark Reflection

Re:Next up Photons Smotons by Anonymous Coward · 2012-10-04 04:55 · Score: 0

Umm, no... there are a lot of ways to detect photons that do not involve exciting states of an atom. For example, Compton scattering doesn't absorb the photon, just bounces an electron off it, in the process giving or taking a non-discrete energy from the photon. That was worked out almost 90 years ago, and is simple enough to be used in undergraduate physics lab courses. Not to mention other processes, like the photoelectric effect with a metal that has bands of energy levels instead of large separated discrete levels, or processes where a photon is scatter off a nucleus. There are even many more ways to create photons without using atomic transitions.

Even if it were true the only way to observe and create photons was via discrete transitions (that had no Doppler shift, no broadening, no uncertainty principle... so light from one transition couldn't trigger a different transition...), such that hypothetical components of a photon could not be detected... then it would not matter. Such a model would give the same predictions as a single component photon model, and there wouldn't be any benefit to using the more complex one.

Failing to understand the concept of system by Giant+Electronic+Bra · 2012-10-04 04:56 · Score: 1

The inside of the box is a system, it is isolated from the outside of the box. It is irrelevant that parts of the system inside the box can measure other parts. Quantum superposition is a relative state, as far as the insides of the box are concerned there is no superposition, but to the observers OUTSIDE, until they exchange information with the inside, the superposition exists. Moreover these superpositions are NOT just artifacts of insufficient knowledge. Bell effectively proved this back in the 60's, though it seems to have taken a few decades for the full implications to dawn on the physics community.

Actually there is again no discussion of an "internal world". That would be a type of 'hidden variable' which is again excluded by Bell and this has been experimentally demonstrated, ther eare no hidden variables. Thus there is no "hidden [...] world that follows reasonable laws". It is indeed "weird all the way down" and we have experimentally verified this.

Of course the REAL thing you guys are all debating here is that it is (supposedly) impossible to create the degree of decoupling of the inside and outside of the box that would be necessary to remain the cat in the superposition for any finite length of time. Of course this is proving to be a rather shaky proposition, as we have now demonstrated superpositions of assemblies of billions of atoms. Albeit these things are much smaller than a cat, but they are nevertheless large enough to (barely) discern with the human eye. How unlikely is it that we will perfect techniques to create cat sized superpositions? I would bet heavily on it being feasible, if difficult.

--
"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson

Re:Failing to understand the concept of system by expatriot · 2012-10-04 07:31 · Score: 1

That is just sophistry. You might as well say that everything in North America is in quantum superposition because I have not measured any of it directly.

Actually... by Giant+Electronic+Bra · 2012-10-04 05:04 · Score: 1

What bothered Einstein wasn't the superposition of dead and alive cats, it was the random nature of the collapse of the wave function in the first place. Einstein couldn't abide the existence of quantum statistics. He was opposed to the existence of the ENSEMBLE of cats. He would say that "God does not play dice" means that the universe is totally deterministic. He was in fact advocating for the existence of hidden variables which would restore causality to QM. Unfortunately for the good doctor Bell removed that possibility from the table decisively. There are no hidden variables, God does indeed figuratively 'roll the dice' and there is no way EVEN IN PRINCIPLE to know if the cat will live or die, even if you had the entire state of the quantum waveform of the whole universe and enough computing power to solve it for the cat's state, that state is still 50% dead and 50% alive, not one or the other.

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"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson

This is the justification for the relational... by Giant+Electronic+Bra · 2012-10-04 05:14 · Score: 2

interpretation. In that interpretation there is no need to consider the question of 'observers'. Quantum states are relative, and to say that a waveform has 'collapsed' is just a statement about its relationship with certain other parts of the system. Thus it is irrelevant that the cat could 'observe itself', this is surely true, but then it is only alive or dead in relationship to itself (and the rest of the inside of the box). To observers outside the box it is in a superposition because that is how they are relating to the part of the system inside the box. Eventually probability dictates that information will leak out and the outside observers relationship to the state inside the box will evolve, they will see the waveform collapse and the cat will become definitely alive or dead to them as well. Note that again this is not just a way of saying that the people outside the box "don't know yet", there are ACTUAL experiments they can perform who's results differ between "don't know" and "waveform hasn't collapsed" (again, Bell Inequalities).

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"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson

Pierre Simon-Laplace forever..... by sgt_doom · 2012-10-04 05:58 · Score: 1

Laplace is still correct, and Prof. Taleb, in his book, The Black Swan, cleverly destroyed this entire uncertainty stuff. At the quantum level, it averages out.

Schrodinger's cat equivelant? by sohmc · 2012-10-04 06:14 · Score: 1

When I try to explain this thought experiment to non-techies (or laymen in general), I use the following:

Imagine a box where you throw in a coin. Close the box and rattle it around. Schrodinger's theory is that the coin is both face up and face down (as seen from the top of the box).

Is this an accurate analogy? Schrodinger's cat had too many pieces and explaining it tended to be too complicated.

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We don't live in Shouldland.

Implications for quantum encryption? by Mike+Van+Pelt · 2012-10-04 06:34 · Score: 1

Getting away from the whole "undead felines" thing, what are the implications for what was supposed to be the next big thing for secure communications, Quantum Encryption?

My understanding of quantum encryption was that what theoretically made it secure was that any attempt to read the data by a man in the middle would necessarily corrupt the data, making the tap obvious. But if the man in the middle is able to read the qbits without changing them, doesn't the whole concept of quantum encryption fail?

Well I deserve credit, dammit! by Vitriol+Angst · 2012-10-04 06:46 · Score: 1

I've been saying for YEARS that the reason we even have this Quantum Uncertainty that some cat likes to pretend is a law of physics, is because the "probing" of quantum states is equivalent to "measuring car movements by launching bowling balls at them".

So "subtler measurements" means you don't disturb the "quantum state"? How obvious is this that it's taken us 20 years?

Quantum theory, while strong on the applied math, seems to be riddled with absolute nonsense as a logical model. They proposed particles being "aware".

I'll also make another prediction; that the very nature of "quantum" or better stated "we can't find an electron halfway between orbital shells" -- is that waves interact with other waves on their peaks, or when in opposite phase. So this entire paradigm of "particles for every force" would also exactly fit "everything is a wave function on some type of medium -- whether you call it Pixels or the Aether."

Anyway, that's my 2 cents on the matter -- but I'm only making sense of it based upon the theory -- not the math. So I'm not going after the "proofs" but the "visualization" of the concepts involved.

"Uncertainty" has always been a problem with measurement -- not with physics itself.

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>>"ad space available -- low rates!!!"

Re:first post ! by Anonymous Coward · 2012-10-04 06:55 · Score: 0

just like families never have 1 kid and a half

I have 1.5 kids you insensitive clod!

Re:first post ! by Beardydog · 2012-10-04 07:01 · Score: 1

Observation doesn't mean that an intelligent agent sees or gains knowledge of the state of the system. A photon is enough of an observer to determine the cat's state. The fact that you could do it with a physicist is mind-bending to consider, but has no importance to the question of what counts as observation.

They've done it to the cat. by Anonymous Coward · 2012-10-04 08:45 · Score: 0

Now they are going to resurrect Schrödinger !

Re:first post ! by Austerity+Empowers · 2012-10-04 09:29 · Score: 1

A cat in a box is always bloody furious, that's what quantum physicists failed to account for.

Not sophistry at all by Giant+Electronic+Bra · 2012-10-04 11:19 · Score: 1

First of all you probably HAVE measured a lot of it. QM is about 'interactions', not some sort of conscious observation. Secondly there's nothing at all odd or wrong with saying that "everything is in superposition with everything else". The ENTIRE UNIVERSE can be described by a single quantum wave form. There is ultimately in QM no such thing as "this thing" and "that thing". You can't even assert that any given electron or proton is a 'certain one' because they are all indistinguishable. Notionally there are many electrons in the universe, but you can as easily assume there is exactly one electron, so what exactly is it that is or isn't in 'superposition' with everything else, or not?

Truly, 99.99% of the way we think about the world is simply not fundamentally applicable to the quantum world. So what is or isn't sophistry when the very concepts of locality, causality, identity, and existence don't apply to the regime we're talking about? This why Feynman said "nobody understands quantum mechanics". He wasn't kidding.

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"Malo periculosam, libertatem quam quietam servitutem." -- Jefferson

quantum error correction, anyone? by Anonymous Coward · 2012-10-04 12:27 · Score: 0

Quantum error correction is likely critical for quantum computing. Why is nobody talking about this?

http://www.nature.com/nature/journal/v490/n7418/full/nature11505.html
http://en.wikipedia.org/wiki/Quantum_error_correction

3.5 by Anonymous Coward · 2012-10-04 12:41 · Score: 0

I could already do this as a first level Cleric, its called "deathwatch"

Re:first post ! by Electricity+Likes+Me · 2012-10-04 19:36 · Score: 1

Except that said photon could also be part of the system. Or more importantly - the alive and dead physicist could do other things like unlock the box and get out of it, becoming a very much alive physicist who has just successfully collapsed their own quantum state.

Re:first post ! by spiralx · 2012-10-04 23:18 · Score: 2

Yes, but if that happens in a locked and windowless room, to observers outside of the room the entire room plus physicist is still in a super-position of alive and dead until they (or the physicist!) open the door to check. For someone outside the building the system of observers outside and the room are in a superposition until they check. See Wigner's friend.

Re:first post ! by gzuckier · 2012-10-05 08:20 · Score: 1

yes but cats do have 9 lives.

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Star Trek transporters are just 3d printers.

agree & theory, tell me what you think by globaljustin · 2012-10-05 09:45 · Score: 1

thnx anon and others...

I agree you cannot transmit classical 'information' that way...also agree getting close is worth investigating

I theorize that yes, it is possible to have true 'quantum communication'...I conjecture that what we know of as 'wormholes' may or may not exist, but I do know that, **if** some kind of 'action at a distance' of two quantum entangled systems can communicate in 1/1 instantaneous Bergsonian time...that thing would probably be like what we classically think of as a 'wormhole' between the two quantum systems...

so basically, my theory would predict a 'quantum communication wormhole' which would behave similar to the theorized space/time wormhole ;)

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Thank you Dave Raggett

Re:first post ! by tolkienfan · 2012-10-05 10:23 · Score: 1

No. An interaction with the photon just entangled it with the system. It's described fully with the Schrodinger equation.
If the authors are actually measuring a quantum state, i.e. not simply a probability, then this implies the cat really Is alive and dead. It's almost a proof of many worlds...

Re:first post ! by Anonymous Coward · 2012-10-05 10:33 · Score: 0

I suggest that simply entangles the quantum state inside the box with the one outside.
From the physists point of view, he collapsed the quantum states of the universe!

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Quantum Measurements Leave Schrödinger's Cat Alive

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