During the early 1900’s, [Einstein] was virtually at war with quantum theory. Its unofficial leader, [Niels Bohr], was constantly rebutting Einstein’s elaborate thought experiments aimed at shooting down quantum theory as a description of reality. It is important to note that [Einstein] did not disagree with the theory entirely, but that he was a realist. And he simply would not believe that reality was statistical in nature, as quantum theory states. He would not deny, for example, that quantum mechanics (QM) could be used to give a probable location of an electron. His beef was with the idea that the electron doesn’t actually have a location until you try to measure it. QM says the electron is in a sort of “superposition” of states, and that asking what this state is without measurement is a meaningless question.
So [Einstein] would dream up these incredibly complex hypothetical thought experiments with the goal of showing that a superposition could not exist. Now, there is something to be said about [Einstein] and his thought experiments. He virtually dreamed up his relativity theory while working as a patent clerk at the ripe old age of 26 years using them. So when he had a “thought” about something, the whole of the scientific world stopped talking and listened. And such was the case on the 4th of May, 1935.
The EPR Paradox
Yes, I know we’ve talked about this before. However, if we want to understand what hidden variables are and why they passed away last Monday (the 24th) , then we need to look at some other details. I encourage you to read our previous discussion of the EPR paper if you have not done so or are unfamiliar with it, as the following paragraphs are going to get a bit heavy.
To reiterate – before we learn what hidden variables are, we need to know what the EPR paper was all about. And to know what the EPR paper was really about, we need to understand the motivation behind it. [Einstein] did not come up with what would become known as the EPR paradox to further knowledge or to shed light on a new idea. It was carefully constructed for one purpose – to put a hole in QM without [Bohr] being able to weasel his way around it, as he had done so many times before. [Einstein] had learned through failed previous thought experiments that [Bohr] was a master at using his measuring instruments against him. [Bohr] would always figure out a way to show how the measuring device disturbed the system and made the entire experiment irrelevant. [Einstein] needed a way to look at the state of particle without disturbing it. And this is exactly what the EPR thought experiment does.
Now, if you have read up on the EPR paradox, you would know that it involves a pair of entangled particles. The particles, because of their entanglement, have an odd property. Any change in a particular property of one particle will be reflected, instantaneously, on the other. This gave [Einstein] the ability to know the state of a quantum particle without directly observing it. It was exactly what he needed to blow a hole wide open in QM.
He separates the two particles over a large distance. He then observes the location or momentum of one of the particles. This forces the shared wave function to collapse, and he is able to know that the other particle (far, far away) has a location or momentum. Somehow the other particle must “know” what measurement [Einstein] has made. “No reasonable definition of reality could be expected to permit this.” the paper would conclude.
There was an alternate theory proposed by the EPR team, and you have probably already guessed what that
theory was. If, during the creation of the entangles particles, there were some type of variables hidden within the two particles that would cement their state, then the entire notion of the superposition could be done away with. Determinism would be restored and there would be no paradox.
Before we move on, it should be noted that the original EPR paper was not worded very well. [Einstein] didn’t actually write it, [Podolsky] did. He would later regret this and go on to say that is was full of formalism that distracted from the main points he wanted to make. Other physicists recognized this, and redid the thought experiment to use more intuitive properties such as electron spin and photon phase as opposed to position / momentum to describe the paradox. This, along with advances in technology would soon allow young scientists to extract the paradox from the realm of imagination and put it to a real world test. And this is where things start get interesting.
It is unlikely that the EPR team or [Bohr] thought about a real world test of the paradox, as they had bigger things to attend to. Others, however, were hard at work playing with the geniuses’ leftovers. If entanglement and its resulting “spooky action at a distance” was real, it would lead to some ground breaking implications. If
[Einstein’s] local variables were real, it would have a major impact on the future of QM. John Bell was one of these men hard at work to solve the paradox. While the Bell Inequalities are worthy of an article on its own, I will summarize them here.
Bell figured out that if local hidden variables existed, they could only explain entanglement up to a certain point. If entanglement could be shown past this point, it could be proven that it was indeed caused by the ‘spooky action’ and not hidden variables. In short, his theory states:
No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.
It is easiest to think of it like this – If you measure the spin of pairs of enough entangled electrons, then you can prove that it was the result of spooky action and not hidden variables. Bell’s Inequality sets the amount you need to measure.
Say Goodbye to the Loopholes
Many have tested the EPR paradox – the first experiment being run in 1981. There have always been loopholes, however, that has kept [Einstein’s] local hidden variables on life support. You see, every single experiment has shown that spooky action is real. There is really some type of connection between entangled particles that is independent of space and time. But the experiments were not perfect. Experiments using entangled photons suffer from the inability to account for all of them. This allows for hidden variables to draw a gasping breath via what is known as the detection loophole. This can be countered by using particles or even atoms, which are easier to keep track of. But it’s difficult to separate entangled particles over long distances, which is needed to ensure communication between the two would have to be faster than light speed, giving rise to the communication loophole.
On August 24, 2015, just a few days ago, a team of researchers released the results of a test that does away with all loopholes. No more can local hidden variables claim to exist. It has taken its last breath and we can conclude what we’ve all known all along – [Einstein] was wrong. The nature of reality is indeed statistical. If you want to find any local hidden variables, you can find them on the same aisle with the aether, cold fusion, and the static universe.
51 thoughts on “The Eulogy Of Local Hidden Variables”
This is very interesting to say the least.
Sure someone will say it is not a hack but who cares?
” [Einstein] was wrong. The nature of reality is indeed statistical.”
You could also say that the things that are being measured (that have a statistical nature) aren’t real. That’s fine too. Saying “ooh, the photon magically had a defined polarization when the other one was measured” (spooky action at a distance, for photons with entangled polarization) could also be rephrased “in an entangled state, the individual polarization of each photon isn’t a real physical thing. It’s only the coupled polarization that’s real.” (This is actually really what you’re forced to abandon when losing locally hidden variables, and what Bell’s theorem tests against.)
A lot of the “spookiness” about quantum mechanics comes from trying to retain the idea that macroscopically “real” things (like, say, position, or the concept of an individual particle) are *always* microscopically real. If, instead, you start thinking like “the only things that are actually real are observed interactions” then it makes a lot more sense. So if you have an interaction that defines the coupled polarization state, then the coupled polarization state is real and fixed, and not distributed. There’s no “spooky action at a distance” because the other photon’s polarization was never real in the first place, so you have no information transfer by defining that interaction.
I guess I need to go read all of their papers to get a better understanding of the problem, but I am curious why this is so astonishing in the first place. The way I see it, the polarity of the electron and positron can be entirely random AND predetermined from the time of measurement without breaking the theory of relativity. Who is to say that the electron-positron pair is randomly created, and each is sent in opposite directions down their respective fiber channels. We have no way of knowing which particle is a positron and which is an electron until we measure one of the particles at the end of its fiber channel. However it is easy to predict that if one is measured to be a positron, then the other will be an electron, not due to some ‘spooky connection’ that breaks special relativity, but instead by the fact that the two particles were decided when they split onto the different fiber channels.
If anything, it seems that the ‘spooky connection’ is just a memory of what state the particle had when it originally split, at the entrance of the fiber channel. If anything, this seems more like evidence against the traditional theory of quantum mechanics, and that in-fact the state of these particles (however unobserved by us) had been decided at the point when they actually split.
“However it is easy to predict that if one is measured to be a positron, then the other will be an electron, not due to some ‘spooky connection’ that breaks special relativity, but instead by the fact that the two particles were decided when they split onto the different fiber channels.”
Nope – that’s actually wrong. That’s what Bell’s theorem tests against. You can actually pretty easily set up math to show that in the case where the states *were* determined at the start, you *don’t* get the same result as quantum mechanics. And quantum’s result is right.
The difference between what *I’m* saying and what you’re saying is that I’m saying “the thing that’s propagating away is *not* an electron with a definite polarization, because in this experiment, you didn’t create one of those – those things aren’t real in this case.” In this case you created an entangled particle, and that entangled state can propagate forever so long as it isn’t disturbed. The entanglement doesn’t allow communication or anything, because the individual polarizations *aren’t real.*
Then what sets the polarization of the other particle when its counterpart is measured?
Bell’s theorems are a “pick one” kind of thing, where you have to choose between localism and realism. Realism means that things are what they are – i.e. they aren’t created ad-hoc by measurement or interaction. Localism means that things are somewhere instead of everywhere or nowhere.
If we reject realism and say the state of the particle doesn’t pre-exist but is instead “created” at the point of measurement, we’re still left with localism which says that both entangled particles must exist separately in space and time instead of being one “entangle-particle” spread over space and time.
We can deal away with realism and with it, hidden variable theories, but we can’t deal away with the idea of localism because empirical observation would break down – you couldn’t isolate systems for observation so you couldn’t test any prediction in any meaningful sense. In other words, if we abandon locality then you cannot say you have measured the particle.
“Then what sets the polarization of the other particle when its counterpart is measured?”
You’re assuming the particle’s polarization is some real thing that gets ‘set’ somehow. It isn’t. Its *individual* polarization only becomes real (definite) when it’s measured. Before that it’s a superposition, coupled with the other particle. It doesn’t have information content on its own.
Its coupled polarization is real (conveys information), because it came from a defined singlet state. So if spin(A) is the spin of one particle, and spin(B) is the spin of the other, you know that spin(A+B) is a real, propagating piece of information. The individual spin of the particles, by themselves, don’t have fully independent existences.
All you know is “interaction(Singlet) = spin(A+B)” produces “interaction with A produces spin(A)”, and requires “interaction with B produces correlated result.” By itself, A doesn’t have enough information to say it came from “Singlet”, so spin(A) conveys no information (it’s randomly distributed). Same for B. But combining the two results gives you the information about the original state.
It doesn’t say that ‘particle A magically changed its polarization.’ It just says that “particle A and B came from a singlet state, and they haven’t interacted with anything else that would indicate their polarization since then.” That’s it.
“we’re still left with localism which says that both entangled particles must exist separately in space and time instead of being one “entangle-particle” spread over space and time.”
This is where the goofy “spooky action” idea comes from. You don’t need it. The polarization of the particle isn’t some ‘real’ thing that has some definite value at some point in spacetime. It’s just a name that people gave to a type of interaction. This is what abandoning realism means – it means humans looked at macroscopic things, like position, time, polarization, identity, etc. and pretended they were fundamentally real. They aren’t.
It doesn’t ‘spread over space and time’: the *information from the original interaction does*. But so does all other kinds of information.
If you measure the spin of a particle, and get “Up”, that just tells you that it’s now in an ‘Up’ state. It doesn’t convey all information about that particle *before*. That’s what I mean by “it isn’t a real thing.” It does convey some information (it tells you it wasn’t in a pure Down state) but the setup of the particle means that you can’t recover all the information about the particle’s creation without both coupled particles.
“You’re assuming the particle’s polarization is some real thing that gets ‘set’ somehow.”
Nope. Realism and locality are two different things.
The measurement must have a certain outcome regardless of the reality of the particle, because the other measurement has a certain outcome. The measurement event is “magically” influenced by something that happens so far away that the influence must travel superluminally.
This problem persists even after the fact that the two parties Alice and Bob cannot exchange information faster than light. This problem exist even after we reject realism and say that the particle has no real position. This problem exists because the probability density wave of the particle must collapse throughout the entire universe at once, and so measuring a particle here means that instantly, without delay, another person trying to measure the same particle there cannot find it. Measurement here determines measurement there and vice versa.
THIS is the spooky action at a distance that Einsten was so worried about. If distant measurement can affect a local measurement instantly, then causality is completely broken down and we can’t gain any meaningful information out of any empirical measurement unless we somehow measure the entire universe at once.
Now that hidden variables and other pre-determinism and communication are ruled out, we cannot but aknowledge that the spooky action problem remains.
And to solve the spooky action problem, theorists have introduced two interpretations: the Copenhagen interpretation which says that the wave function doesn’t actually exist, and the outcome of the entanglement experiment is subjective. This however doesn’t really solve the problem because a distant “reality” is still created upon measurement, and this effect is non-local: something “here” defines something “there” even though not enough time has passed for “there” to have anything to do with “here”.
The other version is the many-worlds interpretation which states that every possibility exists but in a different universe, This is very similiar to Bell’s own third option which he called superdeterminism – that nothing actually happens at all, causality doesn’t exist, and reality is like a film rolling picture after static picture.
“Nope. Realism and locality are two different things.”
Yes. And tossing realism is enough – because then the “non-real” thing can ‘propagate superluminally’ because it’s not real. It’s a shadow – an echo of the original interaction. If I shine a flashlight at the moon, and wave my hand across it, the shadow propagates superluminally across the moon. Big deal.
*Everything* that’s causally connected is an ‘entangled state’ in some sense, because adding *more* information allows you to reconstruct *more* about the original situation.
If a flash of light occurs between two observers, does the photon arriving at one observer “magically influence” the photon arriving at the other observer? Because it has to arrive at the same relative time. Obviously, you wouldn’t say that, right? You would just say “well, the photon’s arrival was pre-arranged the instant it left the flash.” That’s the only difference between the electron spin case and this case: you can’t “pre-program” the discrete spin state. Which only tells you the discrete spin state isn’t real. The only thing that’s real is the interaction in the end.
“The measurement must have a certain outcome regardless of the reality of the particle, because the other measurement has a certain outcome. The measurement event is “magically” influenced by something that happens so far away that the influence must travel superluminally.”
It’s not influenced by that other measurement. You know what it was influenced by? The original decay. Which is causally connected to the first particle.
A lot of the problem here is the difficulty in tossing realism. You have to toss a lot more than you think. You start off by saying “Imagine you have some particle in a spin singlet state that decays.” Well, wait – how did you know you had that state? Unless you’re *already at* the decay’s point in spacetime (or in its prior light cone), you *can’t* know.
So you’re actually starting off as the person on the Earth, shining the flashlight at the moon. You know it’s a spin singlet. Then you measure one, and you know what angle you measured it at. Now you know the other, and you know how the other has to behave as a function of the angle of the spin measurement.
You know what quantum mechanics says about that? It actually says “in order to derive that other spin, you can’t base it on the behavior of electrons in a pure state.” In other words – you *didn’t actually measure some underlying thing about the particle.*
“This problem exists because the probability density wave of the particle must collapse throughout the entire universe at once”
No, it’s not. You’re still thinking about the individual particles separately. That’s the problem. You can’t even *talk* about either of the particles on their own, because the fact that you *know* that their are two particles that came from one decay means you knew another piece of information – a piece that’s causally connected to the second particle. That’s why it’s so hard to abandon realism. But experimentally, it’s easy to do this: you don’t think about abstract crap like “what happens outside of my light cone??” because it’s entirely pointless to think about. Distinct particles in defined states that “pop up” in existence with no connection to their past – it’s all abstractions to make the math easy.
Take the entire experiment in reverse.
Imagine if you just have a spin-detector, and it sees a stream of electrons coming from some distant source. Hm, you say. I wonder what I can learn about this. You can’t learn *anything* about the spin of the source from your current position, and then the source goes away. But then you receive a transmission from Dr. X, on the other side of the source – and magically, he’s made the same detection. He gives you his data, you give him your data, and you *derive* the original spin state based on the observed correlations.
This is exactly the same experiment. And yet I don’t think most people would find it in any way confusing. The confusing part is just still Heisenberg – that you fundamentally *can’t measure* both the “up/down” and “left/right” spin states, so if he measures “up/down” and you measure “left/right,” you can’t just add them. But again, this is just because spin isn’t real – it’s just the interaction of the information from the original decay with your spin measurement apparatus. And it happens to not be linear. Again – big deal.
(I should actually stupidly point out if you do have “up/down” and “left/right” then it *does* work to just add them, because they both predictions give 1/2. So I should’ve said “up/down” and “up-left/down-right”).
Dax you are mistaken. The states never “collapse”. I’d encourage you to look at Consistent Histories. Also Many Worlds and Copenhagen and Consistent Histories all describe the exact same thing but use a different interpretation. They are all the same. Its just about looking at this samenss from a different perspective. Crazyness from MWI, by some people, where every interaction actually creates a universe is a misunderstanding of a maths equation to calculate probablilites actually making real things. But then its a compex topic…
As a reference I suggest these two: (You may regard Lubos as a right wing nutjob but this doesn’t mean his science is bad :))
Best wishes, keep asking questions!
It’s easier to see with the original paradox that is two identical electrons entagled.
As I understand it the idea is to create entagnled electrons you can then either measure the momentum or position of one of them, (the more accurately you do so the less accurate the other becomes by heisenbergs uncertainity principle).
But if they are entagnled and you precisely pin down the momentum of one eletron the position becomes less certain, to prevent you gaining the precise position of it it’s entagnled partner must also now have a precise momentum and less precise position.
In this case the observation causes a change in the electrons quantum state and nessessitates a similar change in it’s partner, this applies to other quantum states (spin included).
So unless the electron knows what you’ll choose to measure before they part ways it can not sneakily set up to know which will be a precise observable and which will be uncertain.
You can know which particle goes which direction. Create an electrical charge field, positive to attract the electron and negative to attract the positron.
What always pisses me off, is when people interpret “observation” in the sense of the mind. Like a spiritual sense.
This isn’t the case is it?
No. Observation means that the entangled state interacted with something to produce a measured value. Said in “basic QM” language, something operated on the entangled state to produce an eigenvalue, forcing the state into an eigenstate.
I prefer to think of it more in information-theory land: ‘observation’ means that something happened to produce information (=entropy) that depends on a state orthogonal to the mixed state. You would lose the QM result if the entangled objects interacted with their environment, for instance – although they have to interact in a way that’s *possible* to measure (even if it’s not *practical*).
Looking at quantum mechanics from an information-theory point of view really helps, because then this ‘spooky distance’ stuff goes away. The only thing that matters is information flow, and that’s easy to understand.
Just one more question, regarding shrodingers cat, obviously there are so many things going on in that box that it seems unlikely there would be no interaction to ruin the quantum state. Does that matter? Or is it simply the case that if we had a magic box which made it impossible for us to get any information from inside the box there would be a superposition?
“Just one more question, regarding shrodingers cat, obviously there are so many things going on in that box that it seems unlikely there would be no interaction to ruin the quantum state. ”
That’s right. It’s a thought experiment. It’s not real.
“Or is it simply the case that if we had a magic box which made it impossible for us to get any information from inside the box there would be a superposition?”
There are two things here that make it impossible: first, it would have to be *impossible* not *impractical*. You can’t build that magic box, at all. You could imagine measuring the gravitational attraction at all points around the box, to determine whether or not the cat is still moving. Or the heat output of the box. Not practical, but possible, which means it’s not a superposition: the information’s already out, so the cat’s in a defined state, not a superposition.
That’s the key with the EPR paradox and Bell’s theorem. Imagine it with electron spins. In that case, you have a pure superposition – it’s impossible to tell what the spin is without measuring it. The state remains undisturbed, or coherent.
An interesting side point to that is this: imagine if you had that magic box. So there’s no way of telling that the cat’s alive. Absolutely none. In that case… what does “alive” mean? If you can’t leave any evidence that you’re actually alive, does it make sense to even use that word?
That’s actually the point that I was making above. Talking about the electron spin of a coupled state by itself is pointless. It doesn’t exist on its own. The interaction that produced it generated 1 “bit” of information – the *coupled* state. Acting on it twice with 2 different experiments will never generate extra information.
Oops, I forgot the second point.
The second point is that there has to be some way to interact with the superposition to produce a different result than interacting with the discrete state. Otherwise the concept of a superposed state is pointless: if you can never measure it, it doesn’t exist. In the Schrodinger’s cat experiment, you can’t interact with the “superposed cat” state to get a different result than “dead cat” or “live cat”, because even if you have your ‘magic box’, inside the box, it “knows” how long it’s been since the cat died, since tons of other stuff happen *after* that happens.
In other words, you never have a superposition of “live cat” and “dead cat”. You’ve got a superposition of “live cat” and a continuum of “cat dead for 1 minute”, “cat dead for 2 minutes”, “cat dead for 3 minutes”, etc, and that state is never “pure” (something that propagates). So there’s no way to interact with some ‘superposition’ to get a result that’s somehow different.
In the EPR-electron spin experiment, that’s not the case. The “mixed spin direction” state remains pure, and there’s an easy way to interact with it- measure it.
I dislike this as well, people make this mistake in quantum mechanics and when thinking about relativity too.
A lot of the reason for that mistake is that early thought experiments assumed that the measuring device had to actually be looked at by a person. It took a long time for the “observer” to become the machine, somewhere between Wheeler’s delayed choice and the quantum eraser proposals, I think.
Not that QM ever assumed that the observer needed to be conscious; just that the publicized thought experiments of the day did. Schrodinger’s cat, for one, assumes that neither the GM tube nor the electronic device nor the feline were able to “observe” the state of the atom or inside the box. Patently untrue, but it helped popularize the idea that the human observer was some how special.
Then there are other experiments, like the Princeton Engineering Anomalies Research (PEAR) that (and a lot of this could be me mis-remembering the papers) seemed to show that a person could affect the generation of random 1s or 0s from a quantum source by “thinking about” the machine. Or, as http://www.princeton.edu/~pear/pdfs/1997-correlations-random-binary-sequences-12-year-review.pdf points out, by “having an intent when starting the measurement”. There’s also http://leyline.org/papers/pdf/Explore.Mass.cons.feb2011.pdf “Effects of Mass Consciousness: Changes in Random Data during Global Events” and http://www.alice.id.tue.nl/references/nelson-2001.pdf CORRELATION OF GLOBAL EVENTS (please ignore the domains, I went with sources from google scholar that had the whole article and not an eliviser login page. These strange bits of research backed by a university line Princeton, and supposedly using QM-based “random event generators” keep giving rise to the “humans affect the quantum world” and “we are quantum beings omg” stories.
Sadly, it would be nice to have a discussion on whether the human brain is deterministic or quantum, what was called quantum brain dynamics in neuroscience. But the whole thing has been polluted by the “quantum mind” crowd’s “consciousness can’t be explained deterministicaly, man, we’re all quantum creatures” chants.
>”There’s no “spooky action at a distance” because the other photon’s polarization was never real in the first place, so you have no information transfer by defining that interaction.”
Yes there is still “spooky action at a distance”. All we’ve established so far is that there are no hidden variables that explain it, which means there must be superluminal influence at a distance. It may not be useful for transmitting information, but there is nevertheless an action at distance because the measurement done on the correlating particle must be influenced by the other distant measurement in order to collapse the particle into the exact opposite state.
This apparent paradox in QM actually comes from the assumption that there exists a non-QM observer who is both local and real, when no such thing can be. When you extend the same laws to the scientists who do the measurement, you’ll see that the measurement of the polarization or spin of the particle do not become real until information has travelled between the two distant parties at less than the speed of light, and so the outcome is decided well after the fact.
At the exact moment when A and B are measuring their respective entangled particles, the outcome of the measurement simply does not exist. When the information of the measurement has had enough time to propagate from A to B and vice versa, this mutual “observation” collapses the system into an internally consistent reality where A measured the opposite of B. For any third observer C then, which way the measurement went is again not real until the information propagates to C, at which point that property of the AB system collapses into a reality ABC… and so forth until the event has propagated through the entire universe and become consistent with all the other events D,E,F,G…
“which means there must be superluminal influence at a distance. ”
This is just needed if you believe that the particle’s spin is somehow “real” and attached to it. The partner gets measured, and suddenly oh! It has to be in this other state in order to match the fact that its origin state was a singlet.
Why does the state have to be something that’s real? It’s just a way to describe the probability density function of a measurement of the system. It doesn’t “propagate”. If you let the particles travel 1 light year apart, then your PDF has to spread over 1 light year. But that’s just the light cone of the original interaction. So all you’re saying is that information from the original interaction can spread out in the PDF in such a way that you *cannot* reconstruct the entire PDF from one point. No big deal.
“This is just needed if you believe that the particle’s spin is somehow “real” and attached to it.”
No. Such belief is not needed. Even if we argue that a particle has no real property, no location, spin, momentum, polarization, charge… anything; two measurements at different locations still depend on each other in a way that has to be “spooky action at a distance”.
If you find a particle in one location, the wavefunction must collapse instantly throughout the entire universe, and that means it instantly cannot be found anywhere else, or if someone else finds it, it instantly means you cannot, which is a violation of locality which says that effects can only propagate at the speed of light.
The point I’m trying to make here is that for two locations in space, A and B that have not yet interacted with each other, a different reality exists where both may have observed the particle to be there because they’ve not yet decided between themselves where the particle is.
Logically then, any given point in space can be interpreted to be its own separate universe where things are always happening in their own ways regardless of the other points, evolving slightly differently from other points.
“The point I’m trying to make here is that for two locations in space, A and B that have not yet interacted with each other, a different reality exists where both may have observed the particle to be there because they’ve not yet decided between themselves where the particle is.”
What makes you think the particle “is” anywhere? What does that even mean? If the particle doesn’t interact with *anything*, how can you define its location at all? It’s an abstract concept.
“Logically then, any given point in space can be interpreted to be its own separate universe where things are always happening in their own ways regardless of the other points, evolving slightly differently from other points.”
If no information propagates between the two, why wouldn’t you consider them to be separate universes? It’s only when you connect the information from the two points that you can derive things about their common past light cone. Not really confusing.
This was my favorite HaD article in a while. Great read!
I don’t think Einstein would be upset, I always thought his adherance to going by what experiments show would mean he would say “well alright, now that we agree I can get to work on this”
Of course the experiment would need to be reproduced by an independent lab to form the conclusion stated by the author, but, it’s pretty neat anyway.
I’m REALLY glad that some people understand this. Because I love LASERs!
Here’s my favorite Quantum joke:
Ah HAHAHA. I didn’t know it would leave off the caption!
“Well, your quantum computer is broken in every way possible simultaneously.”
“Well, your quantum computer is broken in every way possible simultaneously.”
The first line you put above it works as an okay caption too. I thought it was the caption at first. I wasn’t quite sure how it related to the discussion until I saw the actual caption down below.
One way to approach this is that the spooky action isn’t so spooky since the experiment and measurement really start at the time of entanglement. The travel time to separate the objects is part of the communication time, so there is no instantaneous (whatever that means in space-time) action at a distance.
For those who have not some time with QM and matrices of differential equations, “Eigenvalue” is from the German and means characteristic value and eigenstate is characteristic state. Just represents a solution to a matrix equation and associates it with a physical state.
It can be shown that the observation must force the entagled pair to come to an agreement. For example if someone measures the momentum accurately, the pair must decide to therefore reduce certainity in their positions. Ofcourse they decide nothing, the act of taking a precise measurement of the momentum forces the positions to become less defined/ more uncertain if measured. However this proterty becomes shared. Since we pick which to measure they can’t have come to the agreement when they part.
“[Einstein] was wrong” and he did an extremely good job at being wrong! Without people to challenge our theories it becomes easier for us to make assumptions and mistakes. I do not see being wrong in science as a failure. An experiment with a disproved hypothesis can still produce useful data. The hypothesis is not the important part, the important part is the resulting data. The more effort that goes into proving and disproving something the more confident we can be of the result.
“The nature of reality is indeed statistical. If you want to find any local hidden variables, you can find them on the same aisle with the aether, cold fusion, and the static universe.”
Please do not mix everything. On cold fusion there is now a US patent filed by Andrea Rossi and accepted by the American Patent Office on August 25 2015.
The fuel is lithium and the catalyser is nickel!!!!
I think we must avoid burying cold fusion too fast !
You are right but otherwise USPO patent anything so it doesn’t prove it is real.
if you have time, read this report:
” [Einstein] was wrong. The nature of reality is indeed statistical.”
No, it means the nature of reality is non-local. There does exist deterministic non-local theories. One of them is pilot-wave theory, otherwise known as bohmian mechanics.
In fact John Bell was directly inspired by Bohm’s ideas on quantum mechanics when he formulated his famous inequalities.
when will hackaday ever get someone competent at proofreading? this was a rather painful read, as have been many other articles.
Wow, I didn’t see how awesome this article’s content was until you left this completely unhelpful comment regarding writing competency! Thanks!
For more supporting information in a short accurate summation read the top two answers of this stackexchange question and follow the referenced link (in answer 1) to the late Sidney Coleman’s video.
When people talk about “realism” they mean conventional Pre-1920’s non-quantum physics.
The “real” world is quantum.
So, I need this explained to me, if two particles share a state, and share changes in said state, then when you measure one of the particles if the act of measuring it changes it, that change would be reflected in the other particle just the same, whether you touched it or not. so where’s the paradox?
There are several ways to look at it, but I find it easiest to understand that the two particles must somehow know each other’s state no matter the distance between them. The particles could be on opposite sides of the galaxy and they would still be entangled.
Define your acronyms. You never define EPR in this or the other article you linked to, and it doesn’t readily fall out that it means Einstein–Podolsky–Rosen. It’s writing 101, and unlike trivial grammar or spelling issues, it does obfuscate the message.
From the linked article:
“On May 4th, 1935, the New York Times published an article entitled “Einstein Attacks Quantum Theory”, which gave a non technical summary of the [Einstein-Podolsky-Rosen] paper. We shall do something similar.”
If you point out the grammar errors, I will be happy to fix them.
Of course both Einstein and Bohr were wrong. The God doesn’t play dice, but neither do particles behave randomly. What is random is simply in which leg of the pants of time we find ourselves in. Of course there is another version of us in the other leg finding the opposite result, but for either of us the results are all consistent.
I certainly hope we arent in the middle leg!!
What if, the supposed hidden variables are non-local in 3D space, but local at higher dimensions?
Also, let us change perspective on time as a dimension and posit the possibility that, if at any given moment in time the particles become entangles, that point in time will always become a permanent common local variable, this presumes that time is indivisible as a dimension and propagates both into the past and the future in a similar way.
It astounds me that people put so much effort into proving/disproving thought experiments.
Thought experiments are, by their very nature, flawed. Most rely on us “knowing” certain variables, and using that knowledge to show that we can/cannot “know” other variables. As if this could somehow tell us what will happen in reality.
The very concept itself is ridiculous. We CANNOT ever know things about reality because it would require us to know the REAL rules of the system from WITHIN the system itself.
Here is a silly example:
There are 2 more forces more than modern day science accounts for. These two forces always exactly oppose each other at any distance, and therefore perfectly cancel each other out so there is no net observable change.
Prove/Disprove the existence of both forces.
There’s a Bell’s Theorem Avenue really close to where I work.
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