I know they are trying to dumb it down, but I think they are leaving out some fundamental elements of the puzzle here. Bob interprets the message incorrectly sometimes and no reason is offered for why or how often. They say the observers get contradicting answers sometimes, but that revelation seems anticlimactic considering I have no reason the believe Bob's observer should observe outcomes matching Alice's observer any more often than Bob himself can "guess" the result.
I might need to dig into the original paper: https://www.nature.com/articles/s41467-018-05739-8
> There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
> There is another theory which states that this has already happened.
- Douglas Adams, The Restaurant at the End of the Universe
Here's another write-up of the same subject: https://arstechnica.com/science/2018/09/quantum-observers-wi...
"Quantum observers with knowledge of quantum mechanics break reality"
Once one person has flipped the coin, it seems wrong to me to say that an observer outside the box sees a superposition of heads and tails, simply because the person outside the box doesn't know the result of the flip. I don't think that a human's ignorance is equivalent to a waveform superposition.
This is true even if you replace the coin with the results of a quantum random number generator. The problem isn't that the coin is a macroscopic object (and therefore doesn't really do quantum superposition). The problem is that, once observed, there is no uncertainty in the output of the quantum random number generator. There's only human ignorance (for everyone except the one person in the innermost box).
And as I understand it, experiment agrees with me. You take an entangled pair of photons, observe one, and you know what the same observation on the other photon will produce, even if the person making the observation on that photon doesn't.
It could be that the write-up is creating confusion, or that I am confused, but something feels off here (and not just in a "that's too weird to be true" way).
I don't think that it breaks quantum mechanics. It shows once again that the results of the double slit experiments are still not completely understood. That idea in the article only means that the Copenhagen Interpretation is being challenged. It doesn't make all the discoveries in particle physics collapse.
Hold on, what on Earth do they mean by a "quantum message"?
This writeup is incomprehensible. Does anyone know of a better one?
I found this article impossible to make sense of. But what I did gather reminds me of the simultaneity paradox in relativity where it's possible for different observers of two events to perceive their relative order in time differently. So that observer 1 may see event A happen before event B, observer 2 may see event B happen before event A, and observer 3 may see events A and B happen at the same time.
I think people trying to interpret quantum mechanics are mislead by saying that probability wave upon observation collapses to precise value that upon next measurement stays exactly the same. That's unrealistic because no measurement is of perfect precission. Next measurement will give slightly different value. So we really can't tell if we have one exact value or still a probability wave just reshaped to very narrow thing by interaction needed to do the measurement. We can make probability wave wider and fuzzier again just by scattering particle we measure of some other unmeasured particle.
That's how I understand quantum mechanics wave-particle duality. That there's no duality. There are just waves that interact and reshape each other through that interactions. And the only reason that we think of them sometimes as sort of little billiard balls is because annoyingly equations that govern evolution of narrow and sharp probability waves look (not accidentally) exactly the same as primary school level math that governs billard balls.
From the original paper:
>Analysing the experiment under this presumption, we find that one agent, upon observing a particular measurement outcome, must conclude that another agent has predicted the opposite outcome with certainty. The agents’ conclusions, although all derived within quantum theory, are thus inconsistent. This indicates that quantum theory cannot be extrapolated to complex systems, at least not in a straightforward manner.
It really sounds to me that what they're saying is that some phenomena can be described multiple ways. And in particular, it is likely to explain phenomena consistently as X in one setting and Y in another.
This seems akin to the concept of two strings (A and B) being hashed to the same value; the creator of the hash had one value (A) and an observer has a rainbow table that believes the value is different (B) and both are right, but the observer is not able to understand the creator's intention.
Is this analogy roughly correct? And if so, why is this so darn surprising?
Here's my writeup, this is a first-attempt so please offer constructive criticism if wrong:
2 labs (L1 and L2), these are like the box of shrodingers cat, they are in quantum uncertainty.
2 lab workers (Alice, Jane)
2 outside observers (Bob, Frank)
Time is denoted as T0, T1, ...
T0 Alice in Lab1 randomly selects heads / tails
T1 Alice uses heads / tails to setup a quantum particle S
T2 Jane in Lab2 reads the state of S, infers heads / tails and stores this information in a new particle Z
T3 Frank reads the state of Lab2 to infer Z, S, heads/tails and determines pass / fail (pass == was heads), lets call this variable W_frank
T4 Bob reads the state of Lab1 to infer S, heads / tails, and then makes his own pass / fail (pass == was heads) and that's variable W_bob
Since these are separate readings on untangled particles by Bob and Frank, they can get disparate readings W_frank != W_bob
This is a problem since we "collapsed" the state of W_frank -> Z -> S -> Coin, but this doesn't necessarily imply that we can known with certainty that W_bob will match (i.e. forward collapsed Coin -> S -> W_bob).
Basically its just that each lab is in a quantum uncertainty (Quantum Coin is heads/tails, S is in either state, Z is in either state until measured). And making the measurement should reveal this, but there's no guarantee both collapses will result in the same outcome (so in one case the coin was heads, and the other it was tails).
My conclusions:
1. There is no randomness, we just suck at measuring still
2. We are in the "many worlds" but impossible branches can't happen (reality stays consistent somehow) -- so it won't happen even though its theoretically possible
3. The forward collapse does happen, we just haven't done the experiment to verify it. In other words, the pass/fail result would change to keep things consistent (the whole system is entangled). Including the memories everyone would have about it. So maybe this is happening constantly but we just don't know it because it changes even our memories about it.
4. This experiment fractures reality, and we realize we all live in a simulation and that's where "white holes" come from :P
The original Maxwell daemon experiment didn't work because there was some "work" hidden in the formulation.
A few days ago I was reading this https://phys.org/news/2018-09-quantum.html (didn't get on the frontpage), but it's about the difficulty of disappearing quantum information.
As a layman, I can imagine that decoherence plays a similar role in these thought experiments. Maybe perfect transfer of quantum information is impossible.
It would be a nice merge of Schrodinger's cat with Maxwell's daemon. :-D
Thought this might be interesting about many-worlds https://www.hedweb.com/everett/everett.htm#believes if Feynman and Hawking and others are on board with it. I keep seeing with the string theorists and cosmologists that seem to be the leaders in the field are leaning toward many-worlds as the most sensible explanation. It then makes this article seem less interesting if the majority fall into copenhagen but the ones actually doing the real work are more in the many-worlds camp than not.
> And different researchers tend to draw different conclusions. “Most people claim that the experiment shows that their interpretation is the only one that is correct.”
Exactly like in the experiment ...
Edit: To be clearer, why not try to explain the way the paper is received with the very material the paper is about ?
> (Frauchiger has now left academia.)
Tangential: why is that statement in the article?
Our simulation is written in a functional language using lazy evaluation, obviously. Observing a quantum state forces evaluation and consumes more memory on the machine running our simulation. If we observe too much the beings simulating us are going to kill -9 us.
The tao that can be named is not the real tao.
I am happy and sad to hear this.
This write up not only oversimplifies, but it totally neglects one of the more interesting motivations of the original paper [1]. The authors are probing whether or not quantum mechanics is consistent with a single-world interpretation---that is, whether or not there is a unique reality. Formally, the claim is that there is no physical theory that is (1) consistent with QM, (2) consistent with a single-world interpretation, and (3) logically self-consistent.
1. https://arxiv.org/pdf/1604.07422.pdf