The reason you are able to transfer an infinite-complex quantum state over a finite-complex classical communication channel is because the “quantum state” doesn’t even exist, at least not in a single experiment. You can only ever measure it over an ensemble of systems, i.e. infinitely many systems prepared in the same way, as it is a statistical stat only. Your classical measurement results from the qubits to be “teleported” are also random, and you send that classical information over, and then that is used to construct another qubit in a particular state.

Over an ensemble of systems (repeating the experiment an infinite number of times), it’s guaranteed the statistics on the qubit to be “teleported” will be transferred to now be the same as the statistics of the qubit it was “teleported” onto. Hence, you end up transferring the quantum state from one qubit to another using a classical channel. Quantum teleportation is trivial to reproduce in a classical model and it’s not even inherently a “quantum” phenomena, see the Spekkens toy model for example.

It’s not really that horrible of a name, because what the people who coined the term had in mind was something akin to Star Trek teleportation where you are not actually causing the object to disappear and reappear elsewhere nonlocally, but instead you are doing something “destructive” to the original object, transmitting information over a traditional communication channel, and then using that information to reassemble it with different material on the other end. Quantum teleportation is “destructive” to the original qubit in the sense that it places the qubit into a state that no longer matches what you are trying to transmit, but you gain enough information from doing this to transmit it to the other party who can use that information to (statistically) reconstruct the quantum state using their own qubits on their own end.

There are definitely more potential usages than cryptography (not really even sure I’d classify quantum direct communication as a kind of “cryptography” but that’s nitpicking; it doesn’t encrypt anything, it just lets you detect if someone physically disturbed the message in transit), precisely because it does it over a classical channel, that means the transfer would be much more robust to noise (and thus robust to decoherence). You need to establish an entangled Bell pair first before you can perform quantum teleportation which requires a quantum channel, but you can use quantum distillation to transfer many, many Bell pairs over a noisy network and then “distill” out a low-noise Bell pair, and then once you have achieved that you can then use quantum teleportation to transfer over a qubit via a classical communication channel.

I could also see it potentially being useful to transfer quantum information from one medium to another. Let’s say you have qubits encoded in light and qubits encoded in electron spin and you want to transfer a qubit encoded on one onto the other. For example, in this paper they use quantum teleportation to transfer the information from one medium to the next.

Don’t know much in detail but I believe that after the revolution the communists had the brilliant idea to implement a liberal-style competitive multi-party political system, basically the agenda you hear from “democratic socialists” to get communists/socialists in power but maintain with a liberal political system based on multi-party competition. The result was immense factionalization of the communists into a crap ton of different battling parties that resulted in nothing ever getting done, and the main one that is “the government” mainly caring more about trying to hold onto power than actually putting any socialistic policies in place, and people are just kinda getting fed up with a government that doesn’t do jack shit. There are actually more communist parties in the opposition in the parliament than supportive of the government. It just goes to show that “democratic socialism” is a garbage fire, quite literally, the parliament building was set on fire. That is really the extend of my knowledge of it. I have never heard anything positive about the dumpster fire of a political situation there.

We work, to earn the right to work, to earn the right to give, ourselves the right to buy, ourselves the right to live, to earn the right to die.

I never found telling people to read a good insult because like, I know conservatives who read a lot. Stuff like Ann Coulter books and whatever. Anyone can write just about anything, so reading on its own doesn’t automatically make one intelligent.

Americans getting the economy 1 out of 5 of Americans voted for.

Democratic socialism = national socialism. Socialism is democratic by definition, people added “democratic” onto it as a way to distinguish themselves from non-white socialists in the east, and it was originated by the ultranationalist Bernstein who supported German expansionism.

“Did you hear MAGA wants the government to own parts of Intel? That is literally the worst thing they have ever done, they’re so bad they’re literally communists. I wish we could go back to the old days when Republicans were at least respectable and not communists, like Reagan.” 😐

Is JDVance calling on the military to kill himself?

Because promoters of it always treat it like one and suggest that countries should adopt it to guide their policy. If it’s not a comprehensive economic theory then it should not be used to guide policy because it can’t actually made adequate predictions. We couldn’t actually have any confidence at all that any of its claims are correct. If it does not even claim to take into account basic stuff then it should not be taken seriously as an actual economic theory. At best we can say it’s a tentative economic theory that might be interesting to develop further as an intellectual program, but should have no role in actually influencing policy decisions.

For instance, it says nothing about international trade / international balance of payments / currency exchange.

…? How on earth can you have an economic theory that centers around how fiat money works without a comprehensive accounting of international conditions?

People love to be pedantic as an “own” because they think it makes them look smart. And a lot of the times it actually works / is rewarded.

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It’s a myth that Marxism-Leninism says “thou shalt support every national liberation struggle.” If you read Foundations of Leninism it is pretty unambiguously clear that support for national liberation struggles should always be put into the global context of whether doing so supports the overall goals of dismantling imperialism and the global capitalist system or if it hinders it. If you read the book it is quite explicit that we should not support national liberal struggles that go against overall geopolitical interests; i.e. if that national liberation struggle is led and supported by big bourgeois imperialist powers and is being used to facilitate their own interests and so it would set the proletariat back to support it on the global stage. The point is that “national liberation” shouldn’t be treated as some sort of eternal unquestionable moral principle. You should put it into the global context. I don’t know very much about the specific cases you mention, but it is in no way inherently contradictory to Marxism-Leninism to question supporting a particular national liberation struggle. It depends upon their reasoning.

Be unbiased and read Bogdanov’s The Philosophy of Living Experience as well. :)

why is it a child and why is an american on the front-lines in Ukraine

This “oscillation” is called quantum superposition. In practice, the qbit doesn’t oscillate but really has both values at the same time. We call this the quantum state of the qbit.

This is a rather strong metaphysical claim that seems somewhat out of place in an introductory article. It would be like if I’m presenting GR and I say “but spacetime really is like a physical fabric that is actually physically bending and stretching.” You will find many people in the literature, including Einstein himself, who disagree with this notion and would insist that you shouldn’t reify the geometry in spacetime in GR as if it’s a literal physical fabric but is instead a geometric tool used to predict the dispositions of particles. QM has even far more camps on how to properly conceive of the mathematical implications of the mathematics and it’s probably best to not take such a strong stance in an article that is just introducing it, especially since you’re not making it explicitly clear that is just your opinion and so it might mislead people to think that there is some academic consensus that the qubit “really has both values at the same time,” which there is simply not.

You must bombard it with photos. And at quantum scale, a single photon is really huge.

Should this be “bombard with photons”?

If a particle doesn’t interact at all with its environment, it just doesn’t exist by definition.

This is again a metaphysical position, and it’s a bit strange because this is one of the metaphysical postulates of relational quantum mechanics–that all that exists are interactions so if you speak of something independent of interactions then that thing doesn’t actually meaningfully exist–yet relational quantum mechanics has an epistemic view on quantum states and not an ontological view that the particle is in “two states at once.” The contradiction here is clear: you say the particle, when you aren’t interacting/measuring it, is “really has both values at the same time,” but then you also say if it doesn’t interact, “it just doesn’t exist.” Which is it? You have to pick one. There are views that say it “really has both values at the same time,” and in those views it does indeed exist, it exists in a physical superposition of states. There are views that say it does not exist: the particle only exists when it interacts with something, which in those cases it only ever has a single state in relation to what it is interacting with. There are also views that it just has one value and we don’t know what it is.

The particle is in a superposition state, which can be described as “50% 0, 50% 1”. But when we measure it, we won’t have something like 0.5. We have either 0 or 1. And the crazy thing is the qbit then keeps this value after the measure. Meaning several values in a row will all give the same value.

As an interesting side note (not really a critique), if it was just real probabilities, you could actually reproduce a similar effect in a classical model with oscillations. It might indeed be possible to formulate in terms of oscillations, although you would need to introduce something like superdeterminism, time-symmetry, or nonlocality to not run into contradictions with Bell’s theorem. There is already a formulation of quantum computing in the literature that is in terms of classical pendulums with nonlocal connections between them.

This is sadly pseudoscience, that only gets talked about because one smart guy endorsed it, but hardly anyone in academia actually takes it seriously. What you are talking about is called Orch OR, but Orch OR is filled with problems.

One issue is that Orch OR makes a lot of claims that are not obviously connected to one another. The reason this is is an issue is because, while they call the theory “falsifiable” because it makes testable predictions, even if the predictions are tested and it is found to make the correct prediction, that wouldn’t actually even validate the theory because there is no way to actually logically or mathematically connect that experimental validation to all of its postulates.

Orch OR has some rather bizarre premises: (1) Humans can consciously choose to believe things that cannot be mathematically proven, therefore, human consciousness must not be computable, (2) you cannot compute the outcome of a quantum experiment ahead of time, therefore there must be an physical collapse that is fundamentally not computable, (3) since both are not computable, they must be the same thing: physical collapse = consciousness, (4) therefore we should look for evidence that the brain is a quantum computer.

Argument #1 really makes no sense. Humans believing silly things doesn’t prove human decisions aren’t computable. Just look at AI. It is obviously computable and hallucinates nonsense all the time. This dubious argument means that #3 doesn’t follow; there is no good reason to think consciousness and “collapse” are related.

Argument #2 is problematic because physical collapse models are not compatible with special relativity or the statistical predictions of non-relativistic quantum mechanics, and so they cannot reproduce the predictions of quantum field theory in all cases, and so they aren’t particularly popular among physicists, and of course there is no evidence for them. Most physicists see the “collapse” as an epistemic, not a physical, event.

Orch OR also arbitrarily insists on using the Diósi–Penrose model specifically, even though there have been multiple models of physical collapse proposed, such as GRW. There is no obvious reason to use this model specifically, it isn’t connected to any of the premises in the theory. Luckily, argument #2 does present falsifiable claims, but because #2 is not logically connected to the rest of the arguments, even if we do prove that the Diósi–Penrose model is correct, it doesn’t follow that #1, #3, or #4 are correct. We would just know there are physical collapses, but nothing else in the theory would follow.

The only other argument that propose something falsifiable is #4, but again, #4 is not connected to #1, #3, or #4. Even if you desperately searched around frantically for any evidence that the brain is a quantum computer, and found some, that would just be your conclusion: the brain is a quantum computer. From that, #1, #2, and #3 do not then follow. It would just be an isolated fact in and of itself, an interesting discovery but wouldn’t validate the theory. I mean, we already have quantum computers, if you think collapse = consciousness, then you would have to already think quantum computers are conscious. A bizarre conclusion.

In fact, only #2 and #4 are falsifiable, but even if both #2 and #4 are validated, it doesn’t get you to #1 or #3, so the theory as a whole still would remain unvalidated. It is ultimately an unfalsifiable theory but with falsifiable subcomponents. The advocates insist we should focus on the subcomponents as proof it’s a scientific theory because “it’s falsifiable,” but the theory as a whole simply is not falsifiable.

Also, microtubules are structural. They don’t play any role in information processing in the brain, just in binding cells together, but it’s not just brain cells, microtubules are something found throughout your body in all kinds of cells. There is no reason to think at all they play any role in computations in the brain. The only reason you see interest in them from the Orch OR “crowd” (it’s like, what, 2 people who just so happen to be very loud?) is because they’re desperate for anything that vaguely looks like quantum effects in the brain, and so far microtubules are the only things that seem quantum effects may play some role, but this role is again structural. There is no reason to believe it plays any role in information processing or cognition.

Among philosophy academics, it’s somewhat popular to reject the Copenhagen Interpretation of quantum physics – the one we all have an ambient familiarity about that says that the universe is random

It doesn’t, though. The Copenhagen interpretation is not the strong claim that the universe is random, nor is it the strong claim that the universe is predeterministic. Bohr rejected an axiom called that of statistical independence, arguing that in reality it is physically impossible to separate yourself from what you are trying to measure, as you are yourself a physical system that acts on the system through trying to observe it and it acts back on you. He believed this inability to separate yourself from the system creates a limitation in the maximal amount of human knowledge one can gain about a system as gaining knowledge about some parts of a system inherently disturbs and thus erases knowledge about another part, a principle he called the principle of complementarity.

Bohr thus saw quantum mechanics as kind of a “final theory” at the limitations of what is possible for humanity to know about nature, rather than as a direct description of nature as it really is. He once stated that “physics is not about nature, but what we can say about nature.” It wasn’t meant as a strong claim about the underlying ontology of the universe, but instead a position that the underlying ontology is fundamentally unknowable due to the principle of complementarity. Heisenberg agreed due to his uncertainty principle. He did not outright dismiss the possibility that there are hidden variables, but said that even if they exist, the uncertainty principle makes it impossible to measure them, so it is pointless to speculate on them.

The Copenhagen interpretation isn’t the strong claim that the universe is random or not random, but instead the viewpoint that fundamental physical limitations prevent the construction of a measurement device that could actually prove nature in such a way to reveal how it actually is at a fundamental level, and so any speculation regarding that is unfalsifiable and there is no possibility to choose which is correct vs incorrect, so there is no point in such an endeavor. It does leave open the possibility of hidden variables, but does not leave open the possibility (if the interpretation is correct) that there are knowable hidden variables, if an underlying ontology exists, we can’t know it. It’s a claim about epistemic limitations rather than an ontological stance.

When it came to the US, this was largely during WW2 when the Manhattan project was going on. Americans were much more practically minded and not philosophical because they were trying to build something rapidly for a war effort. This led the Copenhagen interpretation to morph from an argument based on physics and philosophy as to why we cannot meaningfully know the universe’s ontology to a purely utilitarian argument that we should “shut up and calculate” because metaphysics is “a waste of time.”

US politics is plagued by American exceptionalism. The overwhelming majority of the population do not even consider how people in other countries view things, and they implicitly assume their own Overton window is the global Overton window of “reasonable discourse.” If anyone disagrees, they literally cannot fathom it is even possible to disagree with American politics, that literally cannot even register in their brain as a possibility, thus they assume you must either be lying or paid to disagree (“wumao” or “Russian bot”). This is why Americans are often so easy to convince that the US should intervene in other countries, because they nearly all implicitly believe that even the citizens of countries like China or Cuba also believe in American politics and are secretly hoping for Americans to come liberate them but are forced to lie about it by their government.

Honestly, I see no way to break this mass delusion without something seriously calling into question American exceptionalism, something that forces Americans to actually take seriously their own position in global politics, which is something I doubt can come internally from the US. It would have to come externally: something in the global geopolitical situation would have to change to force Americans to take seriously the diversity of global politics. It doesn’t even matter if what it is is “socialist,” there just needs to be something that breaks the illusion that US-style politics is the only way to understand the world and the only valid system. You aren’t going to have much luck convincing a population of socialism in a capitalist country where suggesting anything outside of its own media Overton window is considered extremely taboo (which is ironic because if you ask most Americans straight-up if they trust the media, they will say no, but they will almost always defend everything the media says verbatim and act like it is absurd to question it).

I think a lot of proponents of objective collapse would pick a bone with that, haha, although it’s really just semantics. They are proposing extra dynamics that we don’t understand and can’t yet measure.

Any actual physicist would agree objective collapse has to modify the dynamics, because it’s unavoidable when you introduce an objective collapse model and actually look at the mathematics. No one in the physics community would debate GRW or the Diósi–Penrose model technically makes different predictions, however, and in fact the people who have proposed these models often view this as a positive thing since it makes it testable rather than just philosophy.

How the two theories would deviate would depend upon your specific objective collapse model, because they place thresholds in different locations. For GRW, it is based on a stochastic process that increases with probability over time, rather than a sharp threshold, but you still should see statistical deviations between its predictions and quantum mechanics if you can maintain a coherent quantum state for a large amount of time. The DP model has something to do with gravity, which I do not know enough to understand it, but I think the rough idea is if you have sufficient mass/energy in a particular locality it will cause a “collapse,” and so if you can conduct an experiment where that threshold of mass/energy is met, traditional quantum theory would predict the system could still be coherent whereas the DP model would reject that, and so you’d inherently end up with deviations in the predictions.

What’s the definition of interact here?

An interaction is a local event where two systems become correlated with one another as a result of the event.

“The physical process during which O measures the quantity q of the system S implies a physical interaction between O and S. In the process of this interaction, the state of O changes…A quantum description of the state of a system S exists only if some system O (considered as an observer) is actually ‘describing’ S, or, more precisely, has interacted with S…It is possible to compare different views, but the process of comparison is always a physical interaction, and all physical interactions are quantum mechanical in nature.”

The term “observer” is used very broadly in RQM and can apply to even a single particle. It is whatever physical system you are choosing as the basis of a coordinate system to describe other systems in relation to.

Does it have an arbitrary cutoff like in objective collapse?

It has a cutoff but not an arbitrary cutoff. The cutoff is in relation to whatever system participates in an interaction. If you have a system in a superposition of states, and you interact with it, then from your perspective, it is cutoff, because the system now has definite, real values in relation to you. But it does not necessarily have definite, real values in relation to some other isolated system that didn’t interact at all.

You can make a non-separable state as big as you want.

Only in relation to things not participating in the interaction. The moment something enters into participation, the states become separable. Two entangled particles are nonseparable up until you interact with them. Although, even for the two entangled particles, from their “perspectives” on each other, they are separable. It is only nonseparable from the perspective of yourself who has not interacted with them yet. If you interact with them, an additional observer who has not interacted with you or the three particles yet may still describe all three of you in a nonseparble entangled state, up until they interact with it themselves.

This is also the first I’ve heard anything about time-symmetric interpretations. That sounds pretty fascinating. Does it not have experimenter “free will”, or do they sidestep the no-go theorems some other way?

It violates the “free will” assumption because there is no physical possibility of setting up an experiment where the measurement settings cannot potentially influence the system if you take both the time-forwards and time-reverse evolution seriously. We tend to think because we place the measurement device after the initial preparation and that causality only flows in a single time direction, then it’s possible for the initial preparation to affect the measurement device but impossible for the measurement device to affect the initial preparation. But this reasoning doesn’t hold if you drop the postulate of the arrow of time, because in the time-reverse, the measurement interaction is the first interaction in the causal chain and the initial preparation is the second.

Indeed, every single Bell test, if you look at its time-reverse, is unambiguously local and easy to explain classically, because all the final measurements are brought to a single locality, so in the time-reverse, all the information needed to explain the experiment begins in a single locality and evolves towards the initial preparation. Bell tests only appear nonlocal in the time-forwards evolution, and if you discount the time-reverse as having any sort of physical reality, it then forces you to conclude it must either be nonlocal or a real state for the particles independent of observation cannot exist. But if you drop the postulate of the arrow of time, this conclusion no longer follows, although you do end up with genuine retrocausality (as opposed to superdeterminism which only gives you pseudo-retrocausality), so it’s not like it gives you a classical system.

So saying we stick with objective collapse or multiple worlds, what I mean is, could you define a non-Lipschitz continuous potential well (for example) that leads to multiple solutions to a wave equation given the same boundary?

I don’t know, but that is a very interesting question. If you figure it out, I would be interested in the answer.