Physicists just won the Nobel prize for proving that this is true. I’ve read the articles and don’t get it.
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Imagine a magic apple tree. Every year, the apple tree grows exactly two apples, always exactly one green and one red, and flings them each a mile away in opposite directions one to Bob’s house and one to Alice’s house. Which person gets which color of apple is decided randomly.
You’re Alice. You hear the apple fall in your yard. What color is it?
If this is a classical magic apple tree (“classical” meaning “non-quantum”), obviously, you don’t know. But in actual fact it *is* either red or green; it’s just that *you*, Alice, don’t know.
But if this is a quantum magic apple tree, it’s a little different. The apple’s color is *actually* neither red nor green but a superposition of both. It’s not that you personally don’t know which one; it’s that it *actually* is this funny in-between non-color until you go into your yard and look at it. Once you look at it, only then does it become (say) green.
That’s the core of the idea, and the TLDR stops there. But it’s kind of weird, isn’t it? How could you tell the difference between a quantum and a classical magic apple tree?
That’s where Bell’s Inequality comes in (that’s the mathematical/theoretical statement; two of the Nobel Prize winners this year worked on showing the results *experimentally*). It involves entanglement so let’s cover that first. Entanglement just means that if you know the state of one apple, you know (or at least know *better*) what the state of another apple is.
So in this case, Alice and Bob’s apples are *entangled* because Alice initially doesn’t know Bob’s apple’s color, but once she sees her own apple is green, she now immediately knows that Bob’s is red.
The exact math of Bell’s Inequality is a bit complicated to explain here (and doesn’t quite work intuitively for this analogy of apple colors; you’d need to run this on a different set of properties). But the key idea is that Alice and Bob don’t go into the yard and look at the *color* of the apple, but randomly look at some sort of related properties, and then compare what they get with each other. The results for classical magic apple trees would follow Bell’s Inequality, but for quantum magic apple trees they wouldn’t.
By the way, I didn’t touch on the term “local” but we have to add that term as a qualifier because there’s a loophole to Bell’s Inequality where the apples can send each other faster-than-light messages to coordinate their measurement results in the Bell’s Inequality experiments. If we allow for that, we don’t preclude the possibility of a defined (“real”) state that includes inter-apple communication. In fact, that’s the usual interpretation of what’s happening, that entangled apples/particles *instantly* know about the state of their partners – though not without controversy. But it’s worth noting that, if this is indeed how it works, this inter-apple communication cannot be hijacked by humans or anything other than the apples themselves to actually send faster-than-light messages to each other; only the apples themselves would be able to use these messages, and only to coordinate for measurements.
What does this discovery mean for technology? In the press release they mention that it has profound implications, but didn’t list any. Is this the theoretical foundation for quantum computers?
Does this work support the theory that our reality may be a simulation?
A more accurate headline would be “Quantum Mechanics has been proved to the extent of our current ability to prove it.” Thanks to these guys, we know it’s probably not worth it to invest in any more large scale experiments trying to disprove it.
Quantum entanglement is something we’re learning about and using in atomic computers. It’s a way subatomic particles interact. These men set out to prove that there is no “hidden-variable” that was somehow cheating the results in older experiments. Particles really do remain entangled (as if they are communicating, but there is nothing passing between them) across very large distances. Entanglement is easily broken, and other scientists have been working on ways to make it stronger.
The universe is real, no matter where you go. 😂The words were stripped of context to garner attention. So don’t feel silly for not understanding it. It doesn’t make sense.
Actual physicist here to clear a few things up. “Locally real” doesn’t actually mean anything and is a term that has been floating around today because of a pop sci article on Scientific American that is almost complete gibberish that fundamentally misunderstands the issues and is confused about a number of elementary concepts. Here’s an itemized list of what it does wrong and what it should be explaining instead :
– To start, “locally real” doesn’t mean anything. Nor is it pointing to a concept that might itself mean something. The violation of Bell inequalities don’t show that some single thing must be false. Instead they show that one of two things must be false.
– One of those things is “locality”. What this implies is that any point in a physical system is only impacted by other points whose state has had time to reach it. So for example if something is 300,000 kilometers away from me, I’m only impacted by its state one second ago. This is a consequence of special relativity.
– The other thing is “realism”. This one requires delving just a bit into quantum theory. Simply put, the fundamental physical object in the equations of quantum mechanics are not really particles, certainly not in the way laymen imagine them. You don’t compute the properties of some point mass and conclude where it will be at any given point in time. You compute the probability of that. “Realism” is the idea that this is all just theoretical artifact, and that in reality the particle really is somewhere. Our theoretical model gives probabilistic answers, but the idea of “realism” is that there is still a definite answer to the question “where is the particle” at any point in time, and not just at points of measurement.
– What exactly constitutes a measurement is a massive and still very much open debate among experts so there’s simply no way for me to get into it here.
– Bell inequalities are a set of inequalities that, if measured to be violated, show that it is not possible for both “locality” and “realism” to be simultaneously true. Understandably, in the early days of quantum mechanics, physicists had a hard time giving up on “realism”. But Bell showed that if somehow “realism”, as required by basic human intuition, and “locality”, as required by relativistic theory, were both true, then a set of inequalities should hold.
– Experiments have shown that these inequalities do not hold. At this point, you have to abandon either “realism” or “locality”. Again, “locally real” doesn’t mean anything. I would guess most physicists tend to conclude “realism” should be abandoned, but as with measurement these are fairly open ended questions. Quite simply, it’s what quantum theory has been telling you to do all along. There are some non local interpretations of quantum mechanics that preserve realism and are seducing for that reason, but I find them to be very ad-hoc and overly convoluted. There’s also a lot of wiggle room here too if you really understand these issues and play around with them at the border of what’s possible. Personally I like to think there’s some grander theory waiting for us that is globally deterministic but locally probabilistic. Some people refer to that as super-determinism, but I don’t like the term as it implies some difference between determinism and super-determinism (which there isn’t).
Complete layman, but let me see if I’m getting close to gronking this:
1.) A photon is being observed. This is “local reality,” or in other words, “the part of the universe where measurements are being made”. The photon gets split into two. These two are identical to the first and to each other, including orientation and spin.
2.) Somehow the two photons are taken far away from each other and the orientation and/or spin of one is changed by the observer, and immediately the other photon changes in the same way. This is an example of quantum entanglement.
3.) At the time it was discovered, math doesn’t explain this phenomenon so physicists conclude there is either an unknown variable or local reality (the observed particle) doesn’t exist.
4.) Experiments over the ensuing decades identify the loopholes where the variables should be if they do exist.
5.) These Nobel winners did the work proving there were no variables where those loopholes are, ergo: local reality doesn’t exist.
To those who have taken time out of their sweet day to explain this to their best of their abilities… thank you but I’m such a dumb creation of a human and I swear I need a “explain it like a damn newborn”. 😭
The part I don’t understand is that the experiment uses photons which are massless to prove quantum entanglement. Yet all the laymen explanations use cats, apples, dice or other ‘real’ objects with mass to explain it. So what I can’t figure out is what the real world implication of this is. Is a blackhole in one galaxy somehow interacting with a blackhole in another galaxy in ways we don’t know? Is that the point? The idea that an apple isn’t red until I see it doesn’t make any sense to me…its an object with mass so the rules of quantum entanglement don’t apply to the apple, only to the photons reflecting off the apple from some light source. Are there are other types of subatomic particles other than a photon that have no mass? Is quantum entanglement a property associated only with massless particles?
The universe is you.
You are not real because at any given moment in time you are a possibility. A second from now you could be in another state (awake, asleep, happy, miserable, etc). Your self as you observe to be in that state exists at that moment, since you measured the qualities that define you during that brief solidification of reality through your acknowledgment of that state.
You are not local because what you do affects the future, which is a temporal distance that you must traverse to, that cannot be measured until your thoughts and surroundings intertwine to create a reality that cannot be measured in the present, but can be only lived in the moment.
The past you is a reflection of the future you. And the future you is a reflection of the past you. Similar to entangled quantum particles, you can determine one by the other.
Pero char lang ning tanan.
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