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Physicists found a new quantum paradox that casts doubt on a pillar of reality

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Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#71

Post by lisper »

webmaven wrote: post #68
lisper wrote: post #55

Earlier quoted context omitted.

The problem is not copying internal states, the problem is I/O. A given instance of a quantum computation can only be queried once before it decoheres and goes "poof" because the querying process itself decoheres the system. So a quantum computer can never pass the Turing test because it cannot even participate in the Turing test without destroying itself.

> The problem is not copying internal states, the problem is I/O. A given instance of a quantum computation can only be queried once before it decoheres and goes "poof" because the querying process itself decoheres the system. So a quantum computer can never pass the Turing test because it cannot even participate in the Turing test without destroying itself. You seem to be saying that a computer can only be called a…

> You seem to be saying that a computer can only be called a quantum computer if it never decoheres.

Not quite. I'm saying that in the context of using a quantum-computer to play the role of Wigner's friend, it must be isolated from the ultimate observer. If you're not going to require that, you might as well just do the experiment with an actual human.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#72

Post by lisper »

Strilanc wrote: post #65
lisper wrote: post #55

Earlier quoted context omitted.

The problem is not copying internal states, the problem is I/O. A given instance of a quantum computation can only be queried once before it decoheres and goes "poof" because the querying process itself decoheres the system. So a quantum computer can never pass the Turing test because it cannot even participate in the Turing test without destroying itself.

Requiring the the quantum algorithm have literally no interaction with the outside world to count as quantum is a strawman. An AI could use Grover search when trying to find a good enough response. That would be like part of the AI going into and out of superposition for an efficiency boost. Many quantum tasks are more efficient if certain catalyst states are present [1][2]. That would be like a part of the AI stayin…

Let's not lose the plot here: we're talking about a Wigner's-friend-type thought experiment. If you're not going to require that the quantum computer be isolated, then you may just as well use an actual human.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#73

Post by tsimionescu »

henearkr wrote: post #33

The part that seems the most dubious to me is the "choice": > 2. It is possible to make free choices, or at least, statistically random choices. I don't see what would be really compelling in that. If it's false it would just mean that our actions are all kind of mechanistically decided by other events, and that does not shock me. Other point: > 1. When someone observes an event happening, it really happened. What if…

You may say that it's not surprising, but in fact all statistical-style reasoning relies on it. If the universe is superdeterministic, than no kind of statistical reasoning makes any sense, since everything is already set in stone, there is no probability to any event, it has either happened already or will never happen. Since there is no freedom or even randomness, there are no statistically independent events or measurements.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#75

Post by [deleted] »

kmm wrote: post #57
bondarchuk wrote: post #6

The original Wigner's friend paradox: https://en.wikipedia.org/wiki/Wigner%27s_friend The paradox seems to rest on magical thinking about consciousness, and if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved. And, from the article: For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer be…

We're veering away from physics here, but isn't consciousness actually quite "magical". It's beyond remarkable to me that stimulating nervous tissue, composed of quite mundane things like protons and electrons, yields a subjective experience. I know many people reject the hard problem of consciousness, but to those who don't, the implications of thought experiments like Wigner's friend, like superpositions or entangl…

[deleted]

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#76

Post by elwell »

oopsiforgot7 wrote: post #23
canjobear wrote: post #20

Earlier quoted context omitted.

> if one simply accepts that a conscious observer can be in a superposition like any other piece of matter, the paradox is resolved. It’s not so simple. Suppose you’re in a box and observe a quantum experiment, and then I open the box and observe you. Then before I open the box you’re in a superposed state |x> + |y>, corresponding to the two possible outcomes x and y. Fine, no problem so far. But what is your own sub…

If you embrace many worlds all these issues go away.

Only in your world do the issues go away, but in those worlds in which "many worlds" is not true it is maintained as a standing issue.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#77

Post by tsimionescu »

coliveira wrote: post #38
henearkr wrote: post #33

The part that seems the most dubious to me is the "choice": > 2. It is possible to make free choices, or at least, statistically random choices. I don't see what would be really compelling in that. If it's false it would just mean that our actions are all kind of mechanistically decided by other events, and that does not shock me. Other point: > 1. When someone observes an event happening, it really happened. What if…

The main problem of quantum interpretation is the supposed, artificial, distinction between observer and observed system. In a quantum world this distinction is not possible, every event capable of "observing" a system is itself part of the system, modifying it. That's why such interpretations (postulating this separation) give all kinds of strange paradoxes that are impossible to solve. In the quantum world, there i…

Well, the problem is that the reality we observe daily is not at all like quantum reality. We know exactly where our instruments are, even though we know that they are completely stationary. There is no particle/wave duality to tennis balls.

This is the origin of the problem of observation - the predictions of quantum mechanics break down at some point, and we have no idea why. In particular, this happens very clearly when our measurement instruments directly interact with a quantum system, so we call this 'the measurement problem'.

Of course, we can postulate that in fact, despite all of our observations, both subjective and objective, the classical world also behaves quantically but we just can't notice it happening (e.g. the Many Worlds interpretation does this).

We can also say that the quantum world does NOT in fact behave that way, but that the universe is perfectly deterministic and just set up in such a way that we can never observe events that contradict this vision of the universe (superdeterminism claims this - that for example you will always happen to choose the right dial on a measurement apparatus to observe entanglement, but that there is no fundamental reason why that should happen - it could theoretically happen otherwise, but in this universe, ever since the big bang, it has been decided that at some point you will set that dial in the particular way that will make you observe the entanglement result).

There are other theories that postulate that quantum mechanics is in fact deterministic, but very hard to predict, but there are non-local effects (deBroglie-Bohm pilot wave theory is such an example).

We can also ignore the whole hope of trying to understand all this, and simply use the math if and when we need it to predict particle phenomena.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#78

Post by mensetmanusman »

08-15 wrote: post #35

> Take a look at these three statements [...] they cannot all be true Okay, so we have to kill one. The easiest one to kill is > It is possible to make free choices. In other words, quantum mechanics is incompatible with free will. This is clearly shocking to any physicist who believes in Free Will (as defined by philosophers thousands of years ago). But hasn't Free Will been recognized as nonsense for at least two c…

We, the figures of your imaginative simulation, have free will, but have decided that you do not.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#79

Post by elwell »

tsimionescu wrote: post #73
henearkr wrote: post #33

The part that seems the most dubious to me is the "choice": > 2. It is possible to make free choices, or at least, statistically random choices. I don't see what would be really compelling in that. If it's false it would just mean that our actions are all kind of mechanistically decided by other events, and that does not shock me. Other point: > 1. When someone observes an event happening, it really happened. What if…

You may say that it's not surprising, but in fact all statistical-style reasoning relies on it. If the universe is superdeterministic, than no kind of statistical reasoning makes any sense, since everything is already set in stone, there is no probability to any event, it has either happened already or will never happen. Since there is no freedom or even randomness, there are no statistically independent events or me…

> no kind of statistical reasoning makes any sense

Probabilities are useful when you don't have perfect knowledge. But yes, they are an illusion. In truth, every event has a 100% chance of happening. And things that didn't happen aren't real events, they just seemed to be possible, but we were wrong.

Re: Physicists found a new quantum paradox that casts doubt on a pillar of reality

#80

Post by tsimionescu »

08-15 wrote: post #35

> Take a look at these three statements [...] they cannot all be true Okay, so we have to kill one. The easiest one to kill is > It is possible to make free choices. In other words, quantum mechanics is incompatible with free will. This is clearly shocking to any physicist who believes in Free Will (as defined by philosophers thousands of years ago). But hasn't Free Will been recognized as nonsense for at least two c…

In fact, all statistical experiments, from clinical trials to observations of Bell's Inequality depend on the idea that there exists either free will or true randomness (and that we can base our decisions on that source of randomness). If neither exist, then there is no such thing as statistically independent events, and no way to make statistical observations (since that would imply that your choice of what to measure would always be correlated with the result of your measurement).
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