Right. This way of describing it is much closer to "zero-worlds" or relational quantum mechanics, and to my mind is a far simpler, deeper way of understanding what's really going on - reality is simply all entanglement.
What really still gets me is the way it's not simply that the atom wasn't interacted with, but that if the information about the interaction never leaks to the outside world - if it's "erased" after the interaction takes place - then the system still behaves as if the interaction never took place.
It undermines not just the concept that matter really exists, but time as well.
Do you have a source for this "information leaking" concept. I remember hearing about an experiment confirming such an idea, but I can't recall what it was.
I'm not sure the exact experiment performed in the article (which sounded similar), but I've always thought the delayed choice quantum eraser was about the best example of this, once you spend some time understanding the experiment and results:
Can you elaborate on the similarities? I took a course on medieval philosophy and theology (Anselm, Aquinas, Avicenna, and so on) so I am earnestly interested, but the connection isn't jumping out at me.
It addresses the inability of the classical concepts "particle" or "wave" to fully describe the behavior of quantum-scale objects. As Einstein wrote: "It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do"
This is of course extremely interesting and probably important for understanding our universe—but how is it helping anyone to say something like, "...with scientists performing a famous experiment and proving that reality does not exist until it is measured." The statement is like a distraction at a magic show, drawing the reader to the glittery 'reality' and 'exist,' which are totally undefined so the reader's imagination can rove without limit.
Maybe this is really just a fundamental challenge to our assumptions about motion of particles or information transfer in the universe. Isn't that interesting enough without these vague, human aggrandizing assertions about creating reality?
Here's the punch line, space, time and matter are components of a user interface produced through evolution. We don't take the desktop and icons of our computer UI literally and we shouldn't take our evolved UI literally either.
He dialed back the radicalism of his position for his TED Talk. He concludes that consciousness must be something other than computation in the brain, something he just teases in the TED Talk. He spends most of the talk on the less radical Interface Theory of Perception.
If I understand him correctly, he says we don't perceive brains as they really are and therefore brains are not a physical basis of consciousness. Whoa.
The thing is, this isn't even a challenge to any assumptions physicists have, or even a surprising result. Every prediction of quantum theory for these kinds of atomic systems has been borne out.
All this "weirdness" is the same old story of "Is it a particle or a wave?!," when in reality, we know its neither. Quantum objects are represented by wavefunctions, or vectors in a Hilbert space, to which "particle" and "wave" are intuitive approximations in certain regimes, that makes it easier for humans to talk about in natural, non-mathematical language.
All this experiment has shown is that a object that we expect to be described by quantum mechanics turns out to, indeed, be described by quantum mechanics.
You made me remember a comment I made some months ago about the speed of light being a performance optimization on a post asking if reality was a computer simulation.
A lazily computed simulation would lazily compute entities not seeing the laziness. Laziness should have no measurable effect within the simulation, unlike quantum mechanics.
As an analogy, consider Hashlife [1]. It works very differently than your typical game of life implementation... but it still agrees on all the intermediate states! The board won't behave normally for most implementations, but end up in states spelling out "we know we're being cached hierarchically!" when you simulate with hashlife.
You can make an observation of a system whose state is undetermined. By interrogating the system for its state, a state becomes determined. Suppose, for example, that you have a flipped coin and sent it rotating in space, never hitting the floor. Is it heads or is it tails? Until it is looked at, the question doesn't really make sense. And for this case, we'll define "looking at it" to mean sticking out your hand and catching it. There is a probability that it's landed heads up in your hand, and a complimentary probability that it's landed tails up. Once it's in your hand though, you can confidently say which state it's in.
Now, you could definitely take issue with this example, because you could argue that the rotation of the coin is well described, so with initial conditions, you can predict its position at any given moment. But imagine a microscopic quantum system, and, for the sake of this simple explanation, believe that its "rotating through the air" state really does not have any precise heads or tails definition. Until something gets in the way of that system, creating an interaction that exchanges information about its observable state, it's not meaningful to say that it's in one of the observable states at all.
A superpositition of states, as such, is essentially the representation of a state in terms of a basis set of observables. In the case of the coin, heads and tails are the two observable states, they are orthogonal, and they fully represent the state space of the coin. You could flip the coin, and put its state vector into the form of sqrt(2)/2 * Heads + sqrt(2)/2 * Tails. This state isn't observable, but it can be described in terms of observable components, where the coefficients represent the probabilities that a given observable state will be measured upon observation.
> You can make an observation of a system whose state is undetermined. By interrogating the system for its state, a state becomes determined.
For QM, this is not correct, although it's a common misstatement. The correct statement is this: you can make an observation of a system which is not in an eigenstate of the measurement operator you are using. After the measurement, the system is now in an eigenstate of the measurement operator--i.e., the act of measurement changes the state.
Note that this is only true on a collapse interpretation, like Copenhagen. On a no-collapse interpretation, like MWI, the "observation" is just an interaction that entangles the state of the measuring device with the state of the system being measured--it's all just unitary evolution.
> You could flip the coin, and put its state vector into the form of sqrt(2)/2 Heads + sqrt(2)/2 * Tails. This state isn't observable*
Yes, it is; but it isn't observable by a simple method like looking to see if the coin is heads or tails. But according to QM, every state is an eigenstate of some operator, so there will be some observation that will distinguish sqrt(2)/2 * Heads + sqrt(2)/2 * Tails from the state that is exactly orthogonal to it, which is sqrt(2)/2 * Heads - sqrt(2)/2 * Tails.
>The correct statement is this: you can make an observation of a system which is not in an eigenstate of the measurement operator you are using.
I should have distinguished better, but what you're more rigorously calling an eigenstate of a measurement operator, I'm calling an observable state. There is something lost in translation to an audience unfamiliar with terms like eigenstate, but that was my attempt. Would you suggest a better one?
>Note that this is only true on a collapse interpretation, like Copenhagen. On a no-collapse interpretation, like MWI, the "observation" is just an interaction that entangles the state of the measuring device with the state of the system being measured
The greater point being addressed is that MWI is no more deterministic than Copenhagen.
>Yes, it is; but it isn't observable by a simple method like looking to see if the coin is heads or tails. But according to QM, every state is an eigenstate of some operator
Some hermitian operator? But more to the point, if looking at the coin is the only operator at our disposal in the simple example, then its eigenstates are the ones we care about.
> what you're more rigorously calling an eigenstate of a measurement operator, I'm calling an observable state.
Yes, but "observable" here is relative to the measurement you are making. If you make a different measurement (i.e., realize a different operator), then the set of "observable states" by your definition is different, because the set of eigenstates of the operator is different.
> The greater point being addressed is that MWI is no more deterministic than Copenhagen.
But this isn't true. The MWI is completely deterministic, because wave function collapse never occurs, and wave function collapse is the source of all the indeterminism in the Copenhagen interpretation.
> Some hermitian operator?
Yes.
> if looking at the coin is the only operator at our disposal in the simple example, then its eigenstates are the ones we care about.
If all you're interested in is that particular experiment, yes. But here we're discussing claims that must apply to all possible experiments and all possible measurements, not just the particular one in the example you chose. So we have to consider all possible operators and all possible sets of eigenstates, not just the ones in your example.
>But this isn't true. The MWI is completely deterministic, because wave function collapse never occurs, and wave function collapse is the source of all the indeterminism in the Copenhagen interpretation.
For what useful definition of deterministic? If a measurement comes with decoherence into multiple non-inteferring branches, then certainly the state evolves in a predictable way from "god's eye", but not from the perspective of the experiment occupying any given branch.
The definition that says the future state is entirely determined by the present state. That's the only definition I'm aware of.
>the state evolves in a predictable way from "god's eye", not from the perspective of the experiment occupying any given branch.
The entire "god's eye" state is the one that appears in the dynamical laws of QM (unitary evolution), so that's the one that's relevant for assessing determinism.
> the state evolves in a predictable way from "god's eye", but not from the perspective of the experiment occupying any given branch.
This "apparent randomness" of measurement results is equally true of chaotic classical systems; it's not something that only appears in QM. Basically, it's just a consequence of the fact that individual "observers" will in general not have complete knowledge of the state. That doesn't mean the state doesn't evolve deterministically; it just means the observers don't have complete knowledge.
>This "apparent randomness" of measurement results is equally true of chaotic classical systems; it's not something that only appears in QM.
Is that a fair comparison? Yes, in either case, the experimenter is limited in his predictive capability by the information available to him. But in a chaotic system, your predictive power can be improved arbitrarily by surveying more information with greater precision. As I understand it-- and hopefully you can clarify if this is accurate-- decoherence forbids a measurement from receiving information from a branched outcome, so even if you take a measurement with arbitrary access to information now and repeat the same measurement in the future, there becomes a set of information that is fundamentally off limits to the observer in a given branch.
I think so. Perhaps it will help if you look at it this way: you repeat some measurement multiple times, and get a sequence of results that looks random. Is the randomness because of classical chaos, or because of quantum "indeterminacy"? From the measurement results themselves, in many cases, there will be no way to tell. The only case in which there would be a way to tell would be if you specifically made measurements on entangled quantum systems in order to test the Bell inequalities; if those inequalities are violated, the measurements can't be due to classical chaos. But that just underscores my point: looking at "apparent randomness" of measurement results is not sufficient to tell whether they are due to "quantum indeterminacy.
> decoherence forbids a measurement from receiving information from a branched outcome
Once again, this is a misleading way of stating it. What is happening, again, is that the observer evolves into a superposition, corresponding to the superposition that the measured system is in. Decoherence just means the branches of the superposition don't interfere with each other. But the system is still in a single state; the "branches" are not separate states or separate entities, they're parts of a superposition.
(Note, also, that decoherence does not guarantee that the different branches will never interfere with each other. Decoherence is not a fundamental limitation; it's just a recognition of what happens in the usual case, where no special measures are taken to isolate the system or to facilitate interference. According to the MWI, there is in principle always a way to cause the different branches to interfere, i.e., decoherence is never absolute.)
> there becomes a set of information that is fundamentally off limits to the observer in a given branch
According to the MWI, the observers in different branches are not different observers; they're different terms in a superposition that the observer is in. Thinking of them as "different observers" with access to different information implicitly assumes something like the Copenhagen interpretation.
I've always wanted to read (or write?) a book about us determining we are in a simulation, but we find subtle flaws like this we're able to exploit in weird ways. Kind of like breaking out of a VM through register flaws or something. Anyone know of a story along those lines?
I'm reading that book right now, and so far it's good. One can also read: Anathem, Snow Crash, http://qntm.org/ra, or (extremely NSFW) The Metamorphosis of Prime Intellect.
All of them explore the nature of reality and consciousness in some way.
To the parent commenter, please write your story. The world always needs good fiction.
I just finished reading Permutation City a couple weeks ago. Good fun. The core conflict is between two different approaches to modeling, via mimicry of existing systems versus really interesting cellular automata. The automata version doesn't need to 'cheat' in the same way, and is thus a bit harder to find the edges of... (Hopefully that doesn't count as spoilers.)
Maybe you should approach the revelation and "breaking through" by a philosophical rather than logical approach..if we are a simulation the logic we work with is artificial and arbitrary anyway. So in the story, get to the "real reality"...by taking the ideal of what reality should be and comparing it to what is observed to be and somehow "crack" into ultimate reality by doing so.
I think Charlie Stross did a particularly interesting one that happened within a simulation where the characters ultimately discover the enemy they were fighting already won and their simulation ran under a larger simulation. Can't remember the name...
> Kind of like breaking out of a VM through register flaws or something
The difficulty is keeping track of the context while you attempt the exploit. You would have to be able to plant code outside the simulation without causing it to crash.
OTOH, from within, you'd only see a successful attempt to escalate privileges. Imagine being able to edit reality.
I've definitely read one where we're an experiment and the speed of light limit is to stop us from escaping all over the lab equipment. I can't remember what it was called now.
I feel as if fiction where we're in a simulation is relatively common, but one where the hacking of reality is actually done well and plausibly rather than handwaved would be pretty new.
Ah, but how do you know the simulation doesn't just slow down the simulated flow of time so it can keep up? Think of a bullet-time like concept. The universe can be simulated as fast as the underlying hardware can keep up.
But if you're enmeshed in the simulation, you would never notice the slowdown! The only reason the video game is annoying is because we experience time outside of it.
Once you read Teller and Hanrahan's SIGGRAPH paper on potentially-visible set computation, you instantly grok what quantum mechanics is for. At least in an "I want to believe" sense.
How do we go about determining if we are in a lossless compression or not?
I wonder if there is some ordering of "conservation of ---" laws that is strictly enveloping/hierarchical, such that you could choose a level at which to simulate/design a universe.
Most physicists or, depending on who you talk to, nearly half of physicists, would appear to agree with you.
I'm convinced that the Copenhagen interpretation remains popular because by making observation itself an integral part of the theory, you allow us to postulate that there is something special about human brains. But 'mysterious observation' is the luminiferous aether of quantum mechanics.
photonic29: I would like to continue our discussion, but HN has some kind of stupid rule where I can't make more than five posts within a (I think?) 12 hour period. I don't know if this is a general rule that applies to everyone, or simply one of the innumerable passive-aggressive account handicaps our gracious mods will afflict us with if we catch them on a bad day.
At any rate, I can't post anymore for now, so our discussion about MWI and Copenhagen interpretation can't happen. Sorry.
Is that really the case though? An observation collapses a wave function. The Copenhagen interpretation suggests that the collapsed state arises from a probability distribution, but it does not address the "fundamental" origin of that distribution. MW attempts to address it by suggesting that the rest of the reality just went elsewhere, rather than disappearing or never having existed at all, but it still does not explain why "we" get "this" reality. Both rely on observations to collapse the wave function, and neither specifically calls out a conscious agent as necessary for an observation to occur. Observation is a measurement, whether intended and registered by a brain or not.
Not if the MWI is true. Talking about wave function collapse presupposes that the Copenhagen interpretation is true. In the MWI, there is no collapse; it's unitary evolution all the time.
MWI has more than its fair share of physics woo: "QM tells us that everything happens!" and so on. Of course all that's irrelevant to what the MWI interpretation actually says. And likewise with Copenhagen: No respectable physicist thinks that consciousness has any physical effect on quantum systems. Measurements can be taken by machines.
Regardless, the nature of observation really is mysterious. A measurement projects the wavefunction onto an eigenfunction in accordance with Born's rule. MWI does not adequately explain why or how, and Copenhagen simply inserts it as a postulate. Neither is especially satisfying. So the measurement problem is unresolved.
John Wheeler's delayed choice thought experiment was already confirmed in the lab over ten years ago. It's neat that they were able to get results with baryonic matter, and it was definitely worthwhile to try to do that, but this article seems to be implying that the results could have been anything else than what they were, or that there is new physics here, and is wrong on both counts.
Also the deference to the Copenhagen interpretation is annoying - it's wrong. What they've observed is a consequence of how decoherence works, and 'observation' has nothing to do with it. Not faulting the researchers on this but seriously, it's time to stop talking about mythical 'observation' as though it's some integral part of quantum theory.
What does this mean? If there was a supernova eons ago in another galaxy and I'm the only human who had been hit by a cosmic ray, does that mean it didn't exist or happen until ... ?
Does measurement have to include an agent? Could measurement mean interaction with other atoms?
>Does measurement have to include an agent? Could measurement mean interaction with other atoms?
Indeed it can. Roughly put, if information about the state left the undetermined system, a measurement has been made. One of the most frustrating interpretations of literature such as this is the idea that there is something spooky, special, and reality-making about a conscious mind. Lots to think about there philosophically, but the physics happens at lower levels of abstraction.
The trouble with questions like yours is that we're the ones asking them. The results of an unobserved measurement cannot be known, so there's no way to completely remove agency from our experiments.
Personally, I think the simpler and less egocentric view is that all measurements produce wavefunction collapse, even when there's nobody looking.
Is it not possible that it could have been observed no other way? Is observation driving the behaviour or behaviour driving the observation(or an external factor driving both)?
If I'm standing here, all the stuff that the atoms in my body could conceivably interact with have to be backfilled for me to interact with them according to this experiment, but since I'm not special to the universe, atoms three billion light years over, they are still interacting with each other, just not with me. So am I decohered to them? Is this like a divergent timelines theory such that coherence is defined as when different possibilities converge while following possibilities, reducing them and then so must necessarily collapse as other possibilities drop off? So what's the difference between cohered and decohered reality then? It sounds then like it would just be one of those paths, the one that we happen to be on that we only notice because we're conscious so that's our arbitrary (to the universe) observation point. That's the only way I can make sense out of this without attaching significance to human observation.
The philosophical interpretation of Quantum Mechanics is a very hard, unsolved problem. There are many reasons why quantum mechanics is theoretically good and philosophically terrible, and not just in a subtle, esoteric way. The reason is that in Quantum Mechanics there are 2 main types of entities: particles, "things" that evolve according to the Schrodinger equation, and "observers". Observers are what deliver to us the results of randomly sampling from the probability distribution defined by the squared amplitude of the wave function by "collapsing" it, according to the Copenhagen interpretation. However, there is no particle that acts as an observer, they all just follow the Schrodinger equation, but nothing that exists isn't a particle. How could "observers" exist and interact with particles then? The Copenhagen interpretation is philosophically terrible. And it really pisses me off that this article title seems to hint that they've really confirmed it. In a lab, an experimenter can just point to his apparatus and say, "that's the observer". Or, being more formal, they can say a thermodynamically irreversible process plays the role of an observer. But this is not really a satisfying explanation because how could it be possible to generate these large, discontinuous motions we call "collapse" on the macroscale if it is impossible on the microscale? There are the multiverse theories that you seem to describe, but they have their own problems. Rae's Quantum Physics: http://www.amazon.com/Quantum-Physics-Illusion-Reality-Class...
goes over a lot of them without getting to messy in the math. Other interpretations of QM are in the book as well. There are many:
> Observers are what deliver to us the results of randomly sampling from the probability distribution defined by the squared amplitude of the wave function by "collapsing" it, according to the Copenhagen interpretation. However, there is no particle that acts as an observer, they all just follow the Schrodinger equation, but nothing that exists isn't a particle.
This is why proponents of the Many-Worlds Interpretation claim that Occam's razor favours it: you don't need to posit "observers" or "collapses"; there's just the evolution of the wave function.
Occam's razor is not a scientific principle, it's just a rule of thumb. I have yet to see a proof that given a number of equal strength explanations for a phenomenon, the simplest one is always true.
One other thing that's often forgotten is that in Occam's opinion the simplest explanation for everything was God.
armchair musings of a layperson physicist/philosopher follow:
the non-interference pattern is the optimized result of a deterministic universe that requires the observation to occur. The measurement didn't reach back in time, the results were specifically determined by the same causal chain that determined an experiment would be performed.
In the time of Empiricism, the philosophers George Berkeley and John Locke proposed something similar. I believe it was called it immaterialism, or the idea that nothing exists without being perceived. Berkeley went further saying that objects only exist in the mind, or something like that.
They're not saying "nothing exists without being perceived", because the probabilities of things at the quantum level all do exist.
It seems sort of unfortunate that physicists would call these quantum probabilistic behaviors "not reality", because they are just as real as anything else.
Right I'm aware of that. I just thought it was an interesting parallel.
Locke based his works off of the physics known at the time (Newton, etc). His theories were later definitely refuted by advancements in physics. Though it wasn't his intended meaning, it is interesting at least to see similar language being brought back by physics.
One of my favorite authors, Jorge Luis Borges, wrote a short story, "Tlön, Uqbar, Orbis Tertius," based on Berkeleyan philosophy. I thought again of this passage when I read the headline:
"Things duplicate themselves on Tlön; they also tend to grow vague or 'sketchy,' and to lose detail when they begin to be forgotten. The classic example is the doorway that continued to exist so long as a certain beggar frequented it, but which was lost to sight when he died. Sometimes a few birds, or a horse, have saved the ruins of an amphitheater."
Let us not forget about Pilot-Wave theory, where it has both particle and wave-like properties simultaneously. In fact, I don't quite get why people are so enamored by these fanciful interpretations when Pilot-Wave is so much more down-to-earth.
I came here to say the same thing - this behaviour is readily explained by a pilot wave formulation of QM, and requires no spookiness. Increasing number of physicists are re-evaluating Bohm and De Broglie's work - I for one think we've been down a 60 year dead-end, which has yielded models, but no plausible mechanism.
It can be - did a graduate paper on the topic some years ago, looking at it through the Dirac sea - and appears others are taking an interest in the topic too - here's a nice paper which gives a good overview:
I'm not really qualified to talk on a technical level about the matter, but besides the distaste some people have for Aether Theories, there are other reasons some scientists don't like PWT, especially as it's demonstrated by the behaviour of oil droplets.
The physical, conceptual differences between any quantities describing droplets on one side and the wave function on the other side are clear. The former are observable – you may actually measure what the shape of the droplet looks like; you can't measure the wave function by any apparatus, at least not in a single repetition of the experiment. The former has an objective interpretation; the latter has a probabilistic interpretation, and so on. The wave function just encodes all the probability distributions for actual observables – but the wave function isn't and can't be one of them.
I'm not familiar with this particular experiment, but all my pondering on the subject - as a layman - leads me to a simple conclusion.
The properties these experiments are measuring are simply bogus. They are not well defined. The answer that comes out is not some intrinsic property of the "particle", but the result of the environment in which the particle interacted with the "measurement" system, so to speak.
The particle has some other properties, but what's being "measured" is not one of those properties.
How can I explain?
Imagine someone who has never tried any Korean food, and you try to ask him/her: what's your favorite Korean food? There's no answer. So you try to "measure" it by feeding him some Korean items and recording his facial expressions. He will like some items more than others, but it has nothing to do with "his favorite Korean food", and has more to do with how the items were prepared and his mood at the time.
A "point" location for a photon is never defined; it's not a property of a photon that it exists in a point in space. When you fire a photon at a "wall" and see a "blip", you're not seeing the position of the photon at some point in time. You're seeing the rough position of the atom that had an electron that absorbed the photon's energy, and I'm not even sure the atom has a well defined point position either. The whole thing is an artifact (a side effect) of some interaction between several systems and doesn't really tell you anything fundamental about the photon (or the quantum object).
Intuition tells me this is like saying a droplet of water can both be a sphere and a single point because it'll pass through several holes on a net, but capillary action makes it collapse into a needle.
When people talk about hidden variable theories they still assume a definite answer exists.
I'm saying the answer doesn't exist because the question is not really valid in some sense.
Which kind of coincides with the idea that "the observable doesn't exist until measured", but I'm taking a little further and saying, it doesn't exist even when "measured" because you're not really measuring the thing you think you're measuring.
It seems to me there would still be a fact of the matter as to whether the person would enjoy a particular type of food prepared in a certain way, in a certain context, even if that situation never occurs or is considered?
That's the point. Something is the matter of fact, but it's not what the original question was. The original question is bogus. The way you perform the "measurement" influences the answer you get.
Also if you repeat the measurement multiple times, results will change.
From my personal experience, I didn't like soy sauce at first, but then I got used to it and started to really like it.
The topic outlined in the OP's article has been raised before, multiple times, once every couple of years. It was even the focus of a cult indoctrination propaganda piece called "what the bleep do we know".
Essentially, yes, it's bogus science. Quantum physics are much more complex than these articles ever bring on. But by explaining it simply, it sounds awe inspiring and so it propagates across social media. Over and over again.
It isn't that particles exist in multiple states until they are measured. It is that the mechanism by which you measure very small things affects the outcome.
> It isn't that particles exist in multiple states until they are measured.
I thought it was exactly that. Or rather, particles exist in multiple states, and when they are measured, either those multiple states collapse into one (Copenhagen Interpretation) or you, the measurer (who also exists in multiple states), gets entangled with them, causing each of your states to perceive exactly one of the particles' states (Many-Worlds Interpretation).
Unless Bohmian mechanics is correct, in which case no, particles don't exist in multiple states, but do depend on faster-than-light transmission of information about the state of other particles.
I'm personally a really big fan of the Many-Worlds Interpretation. Because a brief abstraction would mean every person will live as long as is physically possible. To outside observers, you may have died at any point along the way.
But, regardless. The copenhagen interpretation is from the 1920's. That isn't to say it's wrong, it's just out of date. It has been expanded upon or replaced since then so why hold onto it, what is the current understanding.
The most important takeaway here is that since measuring very small things affects its outcome, it is currently impossible to know. Articles like this one in the OP bother me because they don't know either. But it always becomes a sensation and spreads misinformation.
> Because a brief abstraction would mean every person will live as long as is physically possible. To outside observers, you may have died at any point along the way.
Though your `life' might not be pretty. It can be maximally awful as long as you can still perceive.
However, we can achieve things using the multi-state characteristics that would be impossible without them. For example, quantum computing. We have confirmed actual speed increases for algorithms using quantum computing which could not happen if the underlying particles were not actually in multiple states.
And perhaps someday we'll get to meet the great programmer in the sky the developed the simulation we are living in and we will ask him why he designed it that way and he will say something like "oh I just wanted to optimize the code so I simply excluded reality subroutines when there were no beings looking. I just never thought you guys would notice. As soon as I saw that you guys noticed the flaw, I was going to load a patch but then the confusion it was causing with the simulated beings became interesting and so I just left it in as an accidental feature of the game."
Meh, but probably not.
I kind of love the idea that it's an optimization because the universe would have a shitty frame rate if light's quantum state wasn't lazily evaluated based on whether anyone's viewport was aimed at it.
Hmm, I figure it's more the the optimizer depends on code not exhibiting undefined behavior, like in C. It's not really the case that it's lazily evaluated, just the the causality gets screwy when you try to observe things in an asynchronous system without any kind of coherent memory model.
The fastest anything can travel is the speed of light, which is the speed perceived when a result is already calculated and held in a CPU cache. For everything else, it must be loaded from RAM, Disk, Network and perhaps also operated upon - which can never be as fast as the speed of light.
Well, the way I understand this, is that this result proves that we do NOT live in a simulation. Because if reality does not exist until measured, then we apparently cannot compute reality ahead of time. And if we cannot compute reality ahead of time, it does not exist yet.
Well, if you want to prove the simulation argument, all you have to do is simulate a reality for an individual at any time-dilation you like. With the parallel compute capabilities we are increasingly growing, simulating a small section of the universe at a large time-dilation should be within our grasp sooner than we think.
There is a limit to the total computation that can be done in the universe or with a certain limited energy/volume of space. It's caused by the slowness of signals traveling at light speed. They say probably a black hole is the best computational engine there is.
I always find it fascinating at just how much of our fundamental physics ends up being constraints on information movement. The laws of thermodynamics are about entropy, general relativity puts constraints on the movement of information (for example, Spooky Action as a Distance(tm) is faster than light, but you can't transmit information with it), the Uncertainty Principle puts limits on how much information you can have on a given system.
Information information everywhere you look in fundamental physics. It does make me wonder why.
It's hard to imagine a universe with infinite resolution. You'd effectively have an infinite number of bits in an infinitely dense space, which would potentially require infinite energy to flip.
But I suspect (on no basis whatsoever, except the fact that all previous metaphors have been wrong) that the "universe = Turing machine model" is wrong in some fundamental ways.
I have no idea what the universe is, but I'm open to the possibility that it isn't just an information processing system.
Agreed, it just feels inadequate to me, too. Information theory is a hammer ... and now everything we can think of (~ information...) looks like a nail.
Another hint that maybe the big Turing machine isn't quite cutting it might be the experiments showing that gravity isn't quite like 'just' an entropic force but seems to behave genuinely different.
I'm fascinated by such things also. I often can't help thinking of God as a programmer, though I don't know how much of that is confirmation bias of my priors as a theist and a programmer. But I've always thought the periodic table and DNA both felt a lot like code...
I think it isn't a coincidence that there is so much order and elegance behind the building blocks of our physical world and the universe but the result is chaotic, and unpredictable.
Maybe it's just our brain discovering patterns that don't mean anything.
Off to be the Wizard by Scott Meyer is a very funny fiction book that is based on the concept of reality being a computer program that hackers can manually manipulate to do cool stuff. It mostly occurs in King Arthur's Court, which happens to be the chosen time and place all these hackers wind up.
That would quite possibly be the worst optimization ever.
"Yeah, I could have tracked and updated n values pretty cheaply, but instead I decided to exponentiate an exponentially huge matrix and use that to update a vector containing 2^n complex numbers associated with the possible assignments of the original n bits. Also, you should use bogosort. It's the best."
Of course. I used that assumption because it was also implicit in the original claim. If we don't have any idea what the top-level rules are, then claiming quantum mechanics is an optimization artifact falls a bit flat.
If the top-level rules are classical-ish, then quantum mechanics is expensive instead of cheap. If the top-level rules are quantum-ish, then that begs the question of why we thought quantum implied simulated. If the top-level rules are totally different... then there's not really much to be concluded.
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[ 28.9 ms ] story [ 3531 ms ] threadThe paper is at http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys.... We changed the URL of this submission from http://www.independent.co.uk/life-style/gadgets-and-tech/new....
So does a thing which is not affecting anything else and not being measured exist? No! QED
see also: https://en.wikipedia.org/wiki/Quantum_Psychology
What really still gets me is the way it's not simply that the atom wasn't interacted with, but that if the information about the interaction never leaks to the outside world - if it's "erased" after the interaction takes place - then the system still behaves as if the interaction never took place.
It undermines not just the concept that matter really exists, but time as well.
https://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser
All that's starting to sound an awful lot like Orthodox Christian theology about the essence of God…
Sounds like that light existed and generated and responded to a gravitational field after it was emitted and before it was detected or measured.
Maybe this is really just a fundamental challenge to our assumptions about motion of particles or information transfer in the universe. Isn't that interesting enough without these vague, human aggrandizing assertions about creating reality?
Check out this TED talk on just that subject. http://www.ted.com/talks/donald_hoffman_do_we_see_reality_as...
Here's the punch line, space, time and matter are components of a user interface produced through evolution. We don't take the desktop and icons of our computer UI literally and we shouldn't take our evolved UI literally either.
The philosophical question would be "what is the controller?"
> Perhaps humanity is the only species burdened with distinguishing the truth.
If I understand him correctly, he says we don't perceive brains as they really are and therefore brains are not a physical basis of consciousness. Whoa.
All this "weirdness" is the same old story of "Is it a particle or a wave?!," when in reality, we know its neither. Quantum objects are represented by wavefunctions, or vectors in a Hilbert space, to which "particle" and "wave" are intuitive approximations in certain regimes, that makes it easier for humans to talk about in natural, non-mathematical language.
All this experiment has shown is that a object that we expect to be described by quantum mechanics turns out to, indeed, be described by quantum mechanics.
https://news.ycombinator.com/item?id=8638150
Lazy loading makes perfect sense to me!
As an analogy, consider Hashlife [1]. It works very differently than your typical game of life implementation... but it still agrees on all the intermediate states! The board won't behave normally for most implementations, but end up in states spelling out "we know we're being cached hierarchically!" when you simulate with hashlife.
1: https://en.wikipedia.org/wiki/Hashlife
Now, you could definitely take issue with this example, because you could argue that the rotation of the coin is well described, so with initial conditions, you can predict its position at any given moment. But imagine a microscopic quantum system, and, for the sake of this simple explanation, believe that its "rotating through the air" state really does not have any precise heads or tails definition. Until something gets in the way of that system, creating an interaction that exchanges information about its observable state, it's not meaningful to say that it's in one of the observable states at all.
A superpositition of states, as such, is essentially the representation of a state in terms of a basis set of observables. In the case of the coin, heads and tails are the two observable states, they are orthogonal, and they fully represent the state space of the coin. You could flip the coin, and put its state vector into the form of sqrt(2)/2 * Heads + sqrt(2)/2 * Tails. This state isn't observable, but it can be described in terms of observable components, where the coefficients represent the probabilities that a given observable state will be measured upon observation.
For QM, this is not correct, although it's a common misstatement. The correct statement is this: you can make an observation of a system which is not in an eigenstate of the measurement operator you are using. After the measurement, the system is now in an eigenstate of the measurement operator--i.e., the act of measurement changes the state.
Note that this is only true on a collapse interpretation, like Copenhagen. On a no-collapse interpretation, like MWI, the "observation" is just an interaction that entangles the state of the measuring device with the state of the system being measured--it's all just unitary evolution.
> You could flip the coin, and put its state vector into the form of sqrt(2)/2 Heads + sqrt(2)/2 * Tails. This state isn't observable*
Yes, it is; but it isn't observable by a simple method like looking to see if the coin is heads or tails. But according to QM, every state is an eigenstate of some operator, so there will be some observation that will distinguish sqrt(2)/2 * Heads + sqrt(2)/2 * Tails from the state that is exactly orthogonal to it, which is sqrt(2)/2 * Heads - sqrt(2)/2 * Tails.
I should have distinguished better, but what you're more rigorously calling an eigenstate of a measurement operator, I'm calling an observable state. There is something lost in translation to an audience unfamiliar with terms like eigenstate, but that was my attempt. Would you suggest a better one?
>Note that this is only true on a collapse interpretation, like Copenhagen. On a no-collapse interpretation, like MWI, the "observation" is just an interaction that entangles the state of the measuring device with the state of the system being measured
The greater point being addressed is that MWI is no more deterministic than Copenhagen.
>Yes, it is; but it isn't observable by a simple method like looking to see if the coin is heads or tails. But according to QM, every state is an eigenstate of some operator
Some hermitian operator? But more to the point, if looking at the coin is the only operator at our disposal in the simple example, then its eigenstates are the ones we care about.
Yes, but "observable" here is relative to the measurement you are making. If you make a different measurement (i.e., realize a different operator), then the set of "observable states" by your definition is different, because the set of eigenstates of the operator is different.
> The greater point being addressed is that MWI is no more deterministic than Copenhagen.
But this isn't true. The MWI is completely deterministic, because wave function collapse never occurs, and wave function collapse is the source of all the indeterminism in the Copenhagen interpretation.
> Some hermitian operator?
Yes.
> if looking at the coin is the only operator at our disposal in the simple example, then its eigenstates are the ones we care about.
If all you're interested in is that particular experiment, yes. But here we're discussing claims that must apply to all possible experiments and all possible measurements, not just the particular one in the example you chose. So we have to consider all possible operators and all possible sets of eigenstates, not just the ones in your example.
For what useful definition of deterministic? If a measurement comes with decoherence into multiple non-inteferring branches, then certainly the state evolves in a predictable way from "god's eye", but not from the perspective of the experiment occupying any given branch.
The definition that says the future state is entirely determined by the present state. That's the only definition I'm aware of.
>the state evolves in a predictable way from "god's eye", not from the perspective of the experiment occupying any given branch.
The entire "god's eye" state is the one that appears in the dynamical laws of QM (unitary evolution), so that's the one that's relevant for assessing determinism.
> the state evolves in a predictable way from "god's eye", but not from the perspective of the experiment occupying any given branch.
This "apparent randomness" of measurement results is equally true of chaotic classical systems; it's not something that only appears in QM. Basically, it's just a consequence of the fact that individual "observers" will in general not have complete knowledge of the state. That doesn't mean the state doesn't evolve deterministically; it just means the observers don't have complete knowledge.
Is that a fair comparison? Yes, in either case, the experimenter is limited in his predictive capability by the information available to him. But in a chaotic system, your predictive power can be improved arbitrarily by surveying more information with greater precision. As I understand it-- and hopefully you can clarify if this is accurate-- decoherence forbids a measurement from receiving information from a branched outcome, so even if you take a measurement with arbitrary access to information now and repeat the same measurement in the future, there becomes a set of information that is fundamentally off limits to the observer in a given branch.
I think so. Perhaps it will help if you look at it this way: you repeat some measurement multiple times, and get a sequence of results that looks random. Is the randomness because of classical chaos, or because of quantum "indeterminacy"? From the measurement results themselves, in many cases, there will be no way to tell. The only case in which there would be a way to tell would be if you specifically made measurements on entangled quantum systems in order to test the Bell inequalities; if those inequalities are violated, the measurements can't be due to classical chaos. But that just underscores my point: looking at "apparent randomness" of measurement results is not sufficient to tell whether they are due to "quantum indeterminacy.
> decoherence forbids a measurement from receiving information from a branched outcome
Once again, this is a misleading way of stating it. What is happening, again, is that the observer evolves into a superposition, corresponding to the superposition that the measured system is in. Decoherence just means the branches of the superposition don't interfere with each other. But the system is still in a single state; the "branches" are not separate states or separate entities, they're parts of a superposition.
(Note, also, that decoherence does not guarantee that the different branches will never interfere with each other. Decoherence is not a fundamental limitation; it's just a recognition of what happens in the usual case, where no special measures are taken to isolate the system or to facilitate interference. According to the MWI, there is in principle always a way to cause the different branches to interfere, i.e., decoherence is never absolute.)
> there becomes a set of information that is fundamentally off limits to the observer in a given branch
According to the MWI, the observers in different branches are not different observers; they're different terms in a superposition that the observer is in. Thinking of them as "different observers" with access to different information implicitly assumes something like the Copenhagen interpretation.
All of them explore the nature of reality and consciousness in some way.
To the parent commenter, please write your story. The world always needs good fiction.
My confusion is a compliment to all three authors.
The difficulty is keeping track of the context while you attempt the exploit. You would have to be able to plant code outside the simulation without causing it to crash.
OTOH, from within, you'd only see a successful attempt to escalate privileges. Imagine being able to edit reality.
I feel as if fiction where we're in a simulation is relatively common, but one where the hacking of reality is actually done well and plausibly rather than handwaved would be pretty new.
The author of Ra also did a short piece you'll probably enjoy: http://qntm.org/responsibility
Good film.
I wonder if there is some ordering of "conservation of ---" laws that is strictly enveloping/hierarchical, such that you could choose a level at which to simulate/design a universe.
I'm convinced that the Copenhagen interpretation remains popular because by making observation itself an integral part of the theory, you allow us to postulate that there is something special about human brains. But 'mysterious observation' is the luminiferous aether of quantum mechanics.
photonic29: I would like to continue our discussion, but HN has some kind of stupid rule where I can't make more than five posts within a (I think?) 12 hour period. I don't know if this is a general rule that applies to everyone, or simply one of the innumerable passive-aggressive account handicaps our gracious mods will afflict us with if we catch them on a bad day.
At any rate, I can't post anymore for now, so our discussion about MWI and Copenhagen interpretation can't happen. Sorry.
Not if the MWI is true. Talking about wave function collapse presupposes that the Copenhagen interpretation is true. In the MWI, there is no collapse; it's unitary evolution all the time.
Regardless, the nature of observation really is mysterious. A measurement projects the wavefunction onto an eigenfunction in accordance with Born's rule. MWI does not adequately explain why or how, and Copenhagen simply inserts it as a postulate. Neither is especially satisfying. So the measurement problem is unresolved.
Also the deference to the Copenhagen interpretation is annoying - it's wrong. What they've observed is a consequence of how decoherence works, and 'observation' has nothing to do with it. Not faulting the researchers on this but seriously, it's time to stop talking about mythical 'observation' as though it's some integral part of quantum theory.
Does measurement have to include an agent? Could measurement mean interaction with other atoms?
Indeed it can. Roughly put, if information about the state left the undetermined system, a measurement has been made. One of the most frustrating interpretations of literature such as this is the idea that there is something spooky, special, and reality-making about a conscious mind. Lots to think about there philosophically, but the physics happens at lower levels of abstraction.
Personally, I think the simpler and less egocentric view is that all measurements produce wavefunction collapse, even when there's nobody looking.
See https://en.wikipedia.org/wiki/Von_Neumann–Wigner_interpretat... and https://en.wikipedia.org/wiki/Measurement_problem if you want to read more.
goes over a lot of them without getting to messy in the math. Other interpretations of QM are in the book as well. There are many:
https://en.wikipedia.org/wiki/Interpretations_of_quantum_mec...
This is why proponents of the Many-Worlds Interpretation claim that Occam's razor favours it: you don't need to posit "observers" or "collapses"; there's just the evolution of the wave function.
Occam's razor is not a scientific principle, it's just a rule of thumb. I have yet to see a proof that given a number of equal strength explanations for a phenomenon, the simplest one is always true.
One other thing that's often forgotten is that in Occam's opinion the simplest explanation for everything was God.
the non-interference pattern is the optimized result of a deterministic universe that requires the observation to occur. The measurement didn't reach back in time, the results were specifically determined by the same causal chain that determined an experiment would be performed.
This "reality doesn't exist until it is measured" business is utterly reprehensible. It is masturbatory science/journalism.
It seems sort of unfortunate that physicists would call these quantum probabilistic behaviors "not reality", because they are just as real as anything else.
Locke based his works off of the physics known at the time (Newton, etc). His theories were later definitely refuted by advancements in physics. Though it wasn't his intended meaning, it is interesting at least to see similar language being brought back by physics.
"Things duplicate themselves on Tlön; they also tend to grow vague or 'sketchy,' and to lose detail when they begin to be forgotten. The classic example is the doorway that continued to exist so long as a certain beggar frequented it, but which was lost to sight when he died. Sometimes a few birds, or a horse, have saved the ruins of an amphitheater."
There was a young man who said, "God
Must think it exceedingly odd
If he finds that this tree
Continues to be
When there's no one about in the Quad."
REPLY
Dear Sir:
Your astonishment's odd:
I am always about in the Quad.
And that's why the tree
Will continue to be,
Since observed by
Yours faithfully,
GOD.
Edit: Formatting (newlines)
http://iopscience.iop.org/1742-6596/306/1/012047/pdf/1742-65...
The physical, conceptual differences between any quantities describing droplets on one side and the wave function on the other side are clear. The former are observable – you may actually measure what the shape of the droplet looks like; you can't measure the wave function by any apparatus, at least not in a single repetition of the experiment. The former has an objective interpretation; the latter has a probabilistic interpretation, and so on. The wave function just encodes all the probability distributions for actual observables – but the wave function isn't and can't be one of them.
http://motls.blogspot.com/2014/07/droplets-and-pilot-waves-v...
I thought the difficulty with pilot-wave theory was that it was difficult, perhaps impossible, to reconcile with special relativity.
What is the conclusion if you are the thing being observed?
The properties these experiments are measuring are simply bogus. They are not well defined. The answer that comes out is not some intrinsic property of the "particle", but the result of the environment in which the particle interacted with the "measurement" system, so to speak.
The particle has some other properties, but what's being "measured" is not one of those properties.
How can I explain?
Imagine someone who has never tried any Korean food, and you try to ask him/her: what's your favorite Korean food? There's no answer. So you try to "measure" it by feeding him some Korean items and recording his facial expressions. He will like some items more than others, but it has nothing to do with "his favorite Korean food", and has more to do with how the items were prepared and his mood at the time.
A "point" location for a photon is never defined; it's not a property of a photon that it exists in a point in space. When you fire a photon at a "wall" and see a "blip", you're not seeing the position of the photon at some point in time. You're seeing the rough position of the atom that had an electron that absorbed the photon's energy, and I'm not even sure the atom has a well defined point position either. The whole thing is an artifact (a side effect) of some interaction between several systems and doesn't really tell you anything fundamental about the photon (or the quantum object).
At least that's how I understand it.
I'm saying the answer doesn't exist because the question is not really valid in some sense.
Which kind of coincides with the idea that "the observable doesn't exist until measured", but I'm taking a little further and saying, it doesn't exist even when "measured" because you're not really measuring the thing you think you're measuring.
Also if you repeat the measurement multiple times, results will change.
From my personal experience, I didn't like soy sauce at first, but then I got used to it and started to really like it.
http://skeptico.blogs.com/skeptico/2005/04/what_the_bleep_.h...
Essentially, yes, it's bogus science. Quantum physics are much more complex than these articles ever bring on. But by explaining it simply, it sounds awe inspiring and so it propagates across social media. Over and over again.
It isn't that particles exist in multiple states until they are measured. It is that the mechanism by which you measure very small things affects the outcome.
I thought it was exactly that. Or rather, particles exist in multiple states, and when they are measured, either those multiple states collapse into one (Copenhagen Interpretation) or you, the measurer (who also exists in multiple states), gets entangled with them, causing each of your states to perceive exactly one of the particles' states (Many-Worlds Interpretation).
Unless Bohmian mechanics is correct, in which case no, particles don't exist in multiple states, but do depend on faster-than-light transmission of information about the state of other particles.
https://en.wikipedia.org/wiki/Quantum_suicide_and_immortalit...
But, regardless. The copenhagen interpretation is from the 1920's. That isn't to say it's wrong, it's just out of date. It has been expanded upon or replaced since then so why hold onto it, what is the current understanding.
The most important takeaway here is that since measuring very small things affects its outcome, it is currently impossible to know. Articles like this one in the OP bother me because they don't know either. But it always becomes a sensation and spreads misinformation.
Though your `life' might not be pretty. It can be maximally awful as long as you can still perceive.
Well, the way I understand this, is that this result proves that we do NOT live in a simulation. Because if reality does not exist until measured, then we apparently cannot compute reality ahead of time. And if we cannot compute reality ahead of time, it does not exist yet.
We don't even know what (free) will is, yet alone whether anyone has it.
Quite sure there's a clever quip about this exact thing in terms of bits and bytes, I just haven't walked into that part of the forest yet.
Edit: I think you're right. Black holes would be the equivalent of a segfault.
https://en.wikipedia.org/wiki/Limits_to_computation
Information information everywhere you look in fundamental physics. It does make me wonder why.
But I suspect (on no basis whatsoever, except the fact that all previous metaphors have been wrong) that the "universe = Turing machine model" is wrong in some fundamental ways.
I have no idea what the universe is, but I'm open to the possibility that it isn't just an information processing system.
Another hint that maybe the big Turing machine isn't quite cutting it might be the experiments showing that gravity isn't quite like 'just' an entropic force but seems to behave genuinely different.
Maybe it's just our brain discovering patterns that don't mean anything.
"Yeah, I could have tracked and updated n values pretty cheaply, but instead I decided to exponentiate an exponentially huge matrix and use that to update a vector containing 2^n complex numbers associated with the possible assignments of the original n bits. Also, you should use bogosort. It's the best."
If the top-level rules are classical-ish, then quantum mechanics is expensive instead of cheap. If the top-level rules are quantum-ish, then that begs the question of why we thought quantum implied simulated. If the top-level rules are totally different... then there's not really much to be concluded.
/jk