bunchberry

@bunchberry@lemmy.world

• ⁨Comment⁩ on ⁨Just one more square bro⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  where can i buy one

• ⁨Comment⁩ on ⁨big facts⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  If you appeal to heat death then you cannot say brains pop back into existence either because “matter has a finite life,” and so it is self-defeating. If brains can pop back into existence due to random fluctuations then surely planets and stars could as well given enough time.

• ⁨Comment⁩ on ⁨big facts⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  It seems more likely in a universe that is infinitely large that brains would come into existence through simpler deterministic processes like they did on earth than random fluctuations no?

• ⁨Comment⁩ on ⁨Can a reasonable person genuinely believe in ghosts?⁩ ⁨⁨2⁩ ⁨months⁩ ago⁩:

  Einstein didn’t even get a nobel prize for special relativity because it was considered too radical at the time.

  He shouldn’t have gotten one for SR specifically anyways because Hendrik Lorentz had already developed a theory that was mathematically equivalent and presented a year prior to Einstein.

  The speed of light can be derived from Maxwell’s equations, which is weird to be able to derive a speed just by analyzing how electromagnetism works, because anyone in any reference frame would derive the same speed, which implies the existence of a universal speed. If the speed is universal, what it is universal to?

  Physicists prior to Einstein believed there might be a universal reference frame which defines absolute time and absolute space, these days called a preferred foliation. The Michelson-Morley experiment was an attempt to measure the existence of this preferred foliation because most theories of how it worked would render it detectable in principle, but found no evidence for it.

  Most physicists these days retell this experiment as having debunked the idea and led to its replacement with Einstein’s special relativity. But the truth is more complicated than that, because Lorentz found you could patch the idea by just assuming objects physically contract based on their motion relative to preferred foliation. Lorentz’s theory was presented in 1904, a year before Einstein, and was mathematically equivalent, so it makes all the same predictions, and so anything Einstein’s theory would predict, his theory would’ve also predicted.

  The reason Lorentz’s theory fell by the wayside is because, by being able to explain the results of the Michelson-Morley experiment which was meant to detect the preferred foliation, it meant it was no longer detectable, and so people liked Einstein’s theory more that threw out this undetectable aspect. But it would still be weird to give Einstein the Nobel prize for what is ultimately just a simplification of Lorentz’s theory.

  But there are also good reasons these days to consider putting the preferred foliation back in. The Friedmann solution to Einstein’s general relativity (the solution associated with the universe we actually live in) spontaneously gives rise to a preferred foliation which is actually empirically observable. You can measure your absolute motion relative to the universe by looking at the cosmic dipole in the cosmic background radiation. Since we know you can measure it now and have actually measured our absolute motion in the universe, the argument against Lorentz’s theory is much weaker.

  An even stronger argument, however, comes from quantum mechanics. A famous theorem by the physicist John Bell proves the impossibility of “local realism,” and in this case locality means locality in terms of special relativity, and realism means belief that particles have real states in the real physical world independently of you looking at them (called the ontic states) which explain what shows up on your measurement device when you try to measure them. Since many physicists are committed to the idea of special relativity, they conclude that Bell’s theorem must debunk realism, that objective reality does not exist independently of you looking at it, and devolve into bizarre quantum mysticism and weirdness.

  But you can equally interpret this to mean that special relativity is wrong and that the preferred foliation needs to put back in. The physicist Hrvoje Nikolic for example published a paper titled “Relativistic QFT from a Bohmian perspective: A proof of concept” showing that you can fit quantum mechanics to a realist theory that reproduces the predictions of relativistic quantum mechanics if you add back in a preferred foliation.

• ⁨Comment⁩ on ⁨Quantum teleportation demonstrated over existing fiber networks — Deutsche Telekom’s T‑Labs used commercially available Qunnect hardware for the demo, claims 90% average accuracy⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  There are nonlocal effects in quantum mechanics but I am not sure I would consider quantum teleportation to be one of them. Despite the fact that the dynamics can be nonlocal, it does not therefore follow that all quantum algorithms are actually implementing nonlocality. Some are just local. Quantum teleportation may look at first glance to be nonlocal but it can be trivially fit to local hidden variable models, such as Spekkens’ toy model, which makes it at least seem to me to belong in the class of local algorithms.

  You have to remember that what is being “transferred” is a statistical description, not something physically tangible, and only observable in a large sample size. Hence, it would be a strange to think that the qubit is like holding a register of its entire quantum state and then that register is disappearing and reappearing on another qubit. The total information in the quantum state only exists in an ensemble.

  In an individual run of the experiment, the qubits may in fact transfer very little information at all between each other, but over the whole ensemble it composes to the quantum state, and thus it then makes sense as to how a joint measurement followed by a transmission of that data over a classical channel could provide sufficient information to move the statistical description of one of the qubits to another entirely locally. Hence, it can be replicated in a local model.

• ⁨Comment⁩ on ⁨I’m a Computing Dummy Who Tried Quantum Coding. Here’s What Happened⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  I got interested in quantum computing because I like computing already (compsci degree) but also because I have an interest in natural philosophy. Answering the question of “what is nature?” obviously requires the input of physics and if you don’t know at least introductory quantum information science then you will not be able to follow along with many important papers on this topic (Bell’s theorem, the Frauchiger-Renner Paradox, the Elitzur-Vaidman paradox, etc). Learning to program for quantum computers gives you an understanding of the overall logical structure of how quantum systems work which then makes it pretty easy to understand those kinds of papers.

• ⁨Comment⁩ on ⁨America Isn’t Ready for What AI Will Do to Jobs⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  Moore’s law died a long time ago. Engineers pretended it was going on for years by abusing the nanometer metric, by saying that if they cleverly find a way to use the space more effectively then it is as if they packed more transistors into the same nanometers of space, and so they would say it’s a smaller nanometer process node, even though quite literal they did not shrink the transistor size and increase the number of transistors on a single node.

  This actually started to happen around 2015. These clever tricks were always exaggerated because there isn’t an objective metric to say that a particular trick on a 20nm node really gets you performance equivalent to 14nm node, so it gave you huge leeway for exaggeration. In reality, actual performance gains drastically have started to slow down since then, and the cracks have really started to show when you look at the 5000 series GPUs from Nvidia.

  The 5090 is only super powerful because the die size is larger so it fits more transistors on the die, not because they actually fit more per nanometer. If you account for the die size, it’s actually even less efficient than the 4090 and significantly less efficient than the 3090. In order to pretend there have been upgrades, Nvidia has been releasing software for the GPUs for AI frame rendering and artificially locking the AI software behind the newer series GPUs. The program Lossless Scaling proves that you can in theory run AI frame rendering on any GPU, even ones from over a decade ago, and that Nvidia’s locking of it behind a specific GPU is not hardware limitation but them trying to make up for lack of actual improvements in the GPU die.

  Chip improvements have drastically slowed done for over a decade now and the industry just keeps trying to paper it over.

• ⁨Comment⁩ on ⁨it's a long distance relationship⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  There is no limit to entanglement as everything is constantly interacting with each other and spreading the entanglement around. That is in fact what decoherence is about, because spreading the entanglement throughout trillions of particles in the environment dilutes it such that quantum interference effects are to subtle to notice, but they are all technically entangled. So if you think entanglement means things are one entity, then you pretty much have to treat the whole universe as one entity. That was the position of Bohm and Blokhintsiev.

• ⁨Comment⁩ on ⁨Save as PDF⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  the world is run by PDF files

• ⁨Comment⁩ on ⁨Not that limit⁩ ⁨⁨3⁩ ⁨months⁩ ago⁩:

  ChatGPT just gives the correct answer that the limit doesn’t exist.

• ⁨Comment⁩ on ⁨I'm good, thanks⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:

  Depends upon what you mean by realism. If you just mean belief in a physical reality independent of a conscious observer, I am not really of the opinion you need MWI to have a philosophically realist perspective.

  For some reason, everyone intuitively accepts the relativity of time and space in special relativity as an ontological feature of the world, but when it comes to the relativity of the quantum state, people’s brains explode and they start treating it like it has to do with “consciousness” or “subjectivity” or something and that if you accept it then you’re somehow denying the existence of objective reality. I have seen this kind of mentality throughout the literature and it has never made sense to me.

  Even Eugene Wigner did this, when he proposed the “Wigner’s friend” thought experiment, he points out how two different observers can come to describe the same system differently, and then concludes that proves quantum mechanics is deeply connected to “consciousness.” But we have known that two observers can describe the same system differently since Galileo first introduced the concept of relativity back in 1632. There is no reason to take it as having anything to do with consciousness or subjectivity or anything like that.

  (You can also treat the wavefunction nomologically as well, and then the nomological behavior you’d expect from particles would be relative, but the ontological-nomological distinction is maybe getting too much into the weeds of philosophy here.)

  I am partial to the way the physicist Francois-Igor Pris puts it. Reality exists as independently of the conscious observer, but not independently from context. You have to specify the context in which you are making an ontological claim for it to have physical meaning. This context can be that of the perspective of a conscious observer, but nothing about the observer is intrinsic here, what is intrinsic is the context, and that is just one of many possible contexts an ontological claim can be made. Two observers can describe the same train to be traveling at different velocities, not because they are conscious observers, but because they are describing the same train from different contexts.

  The philosopher Jocelyn Benoist and the physicist Francois-Igor Pris have argued that the natural world does have a kind of an inherent observer-observed divide but that these terms are misleading being “subject” tends to imply a human subject and “observer” tends to imply a conscious observer, and that a lot of the confusion is cleared up once you figure out how to describe this divide in a more neutral, non-anthropomorphic way, which they settle on talking about the “reality” and the “context.” The reality of the velocity of the train will be different in different contexts. You don’t have to invoke “observer-dependence” to describe relativity. Hence, you can indeed describe quantum theory as a theory of physical reality independent of the observer.

• ⁨Comment⁩ on ⁨I'm good, thanks⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:

  MWI very specifically commits to the existence of a universal wavefunction. Everett’s original paper is literally titled “The Theory of the Universal Wavefunction.” If you instead only take relative states seriously, that position is much closer to relational quantum mechanics. In fact, Carlo Rovelli explicitly describes RQM as adopting Everett’s relative-state idea while rejecting the notion of a universal quantum state.

  MWI claims there exists a universal quantum state, but quantum theory works perfectly well without this assumption if quantum states are taken to be fundamentally relative. Every quantum state is defined in relation to something else, which is made clear by the Wigner’s friend scenario where different observers legitimately assign different states to the same system. If states are fundamentally relative, then a “universal” quantum state makes about as much sense as a “universal velocity” in Galilean relativity.

  You could arbitrarily choose a reference frame in Galilean relativity and declare it universal, but this requires an extra postulate, is unnecessary for the theory, and is completely arbitrary. Likewise, you could pick some observer’s perspective and call that the universal wavefunction, but there is no non-arbitrary reason to privilege it. That wavefunction would still be relative to that observer, just with special status assigned by fiat.

  Worse, such a perspective could never truly be universal because it could not include itself. To do that you would need another external perspective, leading to infinite regress. You never obtain a quantum state that includes the entire universe. Any state you define is always relative to something within the universe, unless you define it relative to something outside of the universe, but at that point you are talking about God and not science.

  The analogy to Galilean relativity actually is too kind. Galilean relativity relies on Euclidean space as a background, allowing an external viewpoint fixed to empty coordinates. Hilbert space is not a background space at all; it is always defined in terms of physical systems. You can transform perspectives in spacetime, but there is no transformation to a background perspective in Hilbert space because no such background exists. The closet that exists is a statistical transformation to different perspectives within Liouville space, but this only works for objects within the space; you cannot transform to the perspective of the background itself as it is not a background space.

• ⁨Comment⁩ on ⁨I'm good, thanks⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:
  1. Entanglement is just a mathematical property of the theory. If it is sufficient to explain measurement then there is not anything particularly unique about MWI since you can employ this explanation within anything. You also say I missed your point by repeating exactly what I said.
  2. You’re the one giving this bullet point list as if you are debunking all of my points one-by-one. If you agree there is nothing especially “more local” about MWI than any other interpretation then why not just ignore that point and move on?
  3. A relative state is not an entangled state. Again you need to read the papers I linked. We are talking about observer-dependence in the sense of how the velocity of a train in Galilean relativity can be said to have a different value simultaneously for two different observers. I drew the direct comparison here in order to explain that in my first comment. This isn’t about special relativity or general relativity, but about “relativity” in a more abstract sense of things which are only meaningfully defined as a relational property between systems. The quantum state observer A assigns to a system can be different from the quantum state observer B assigns to the system (see the Wigner’s friend thought experiment). The quantum state in quantum mechanics is clearly relative in this sense, and to claim there is a universal quantum state requires an additional leap which is never mathematically justified.
  4. Please for the love of god just scroll up and read what I actually wrote in that first post and respond to it. Or don’t. You clearly seem to be entirely uninterested in a serious conversation. I assume you have an emotional attachment to MWI without even having read Everett’s papers and getting too defensive that you refuse to engage seriously in anything I say, so I am ending this conversation here.
• ⁨Comment⁩ on ⁨I'm good, thanks⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:
  1. Not sure what this first point means. To describe decoherence you need something like density matrix notation or Liouville notation which is mathematically much more complicated. For example, a qubit’s state vector grows by 2^N, but if you represent it in Liouville notation then the vector grows by 4^N. It is far more mathematically complicated as a description. Your second point also agrees with me. We know the Born rule is real because we can observe real outcomes on measurement devices, something which MWI denies exists.
  2. This is also true in Copenhagen. Again, if that’s your criterion for locality then Copenhagen is also local.
  3. I think you should read Everett’s papers “‘Relative State’ Formulation of Quantum Mechanics” and “The Theory of the Universal Wave Function” to see the difference between wavefunctions defined in a relative sense vs a universal sense. You will encounter this with any paper on the topic. I’m a bit surprised you genuinely have never heard of the concept of the universal wavefunction yet are defending MWI?
  4. That quotation does not come one iota close to even having the air of giving the impression of loosely responding to what I wrote. You are not seriously engaging with what I wrote at all.
• ⁨Comment⁩ on ⁨I'm good, thanks⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:

  The Many Worlds interpretation is rather unconvincing to me for many reasons.

  |1| It claims it is “simpler” just by dropping the Born rule, but it is mathematically impossible to derive the Born rule from the Schrodinger equation alone. You must include some additional assumption to derive it, and so it ends up necessarily having to introduce an additional postulate at some point to derive the Born rule from. Its number of assumptions thus always equal that of any other interpretation but with additional mathematical complexity caused by the derivation.

  • arxiv.org/abs/2402.17066

  |2| It claims to be “local” because there is no nonlocal wavefunction collapse. But the EPR paper already proves it’s mathematically impossible for something to match the predictions of quantum theory and be causally local if there are no hidden variables. This is obscured by the fact that MWI proponents like to claim the Born rule probabilities are a subjective illusion and not physically rule, but illusions still have a physical cause that need to be physically explained, and any explanation you give must reproduce Born rule probabilities, and thus must violate causal locality. Some MWI proponents try to get around this by redefining locality in terms of relativistic locality, but even Copenhagen is local in that sense, so you end up with no benefits over Copenhagen if you accept that redefinition.

  • arxiv.org/abs/0706.2661v1
  • arxiv.org/abs/2306.07794

  |3| It relies on belief that there exists an additional mathematical entity Ψ as opposed to just ψ, but there exists no mathematical definition or derivation of this entity. Even Everett agreed that all the little ψ we work with in quantum theory are relative states, but then he proposes that there exists an absolute universal Ψ, but to me this makes about as much sense as claiming there exists a universal velocity in Galilean relativity. There is no way to combine relative velocities to give you a universal velocity, they are just fundamentally relative. Similarly, wavefunctions in quantum mechanics are fundamentally relative. A universal wavefunction does not meaningfully exist.

  • arxiv.org/abs/2012.05712

  |4| You describe MWI as kind of a copying of the world into different branches where different observers see different outcomes of the experiment, but that is not what MWI actually claims. MWI claims the Born rule is a subjective illusion and all that exists is the Schrodinger equation, but the Schrodinger equation never branches. If, for example, a photon hits a beam splitter with a 50% chance of passing through and a 50% chance of being reflected and you have a detector on either side, the Schrodinger equation will never evolve into a state that looks anything like it having past through or it having been reflected. Indeed, even those probabilities I gave you come from the Born rule.

  This was something Einstein pointed out in relation to atomic decay, that no matter how long you evolve the Schrodinger equation, it never evolves into a state that looks anything like decay vs non-decay. If the universe really is just the Schrodinger equation, you simply cannot say that it branches into two “worlds” where in one you see one outcome and in another you see a different outcome, because the Schrodinger equation never gives you that. You would have to claim that the entire world consists of a single evolving infinite-dimensional universal wavefunction that is nothing akin to anything we have ever observed before.

  There is a good lecture below by Maudlin on this problem, that MWI presents a theory which has no connection to observable reality because nothing within the theory contains any observables.

  www.youtube.com/watch?v=us7gbWWPUsA

  Rovelli also comments on it:

  The gigantic, universal ψ wave that contains all the possible worlds is like Hegel’s dark night in which all cows are black: it does not account, per se, for the phenomenological reality that we actually observe. In order to describe the phenomena that we observe, other mathematical elements are needed besides ψ: the individual variables, like X and P, that we use to describe the world. The Many Worlds interpretation does not explain them clearly. It is not enough to know the ψ wave and Schrödinger’s equation in order to define and use quantum theory: we need to specify an algebra of observables, otherwise we cannot calculate anything and there is no relation with the phenomena of our experience. The role of this algebra of observables, which is extremely clear in other interpretations, is not at all clear in the Many Worlds interpretation.
  

  — Carlo Rovelli, “Helgoland: Making Sense of the Quantum Revolution”

• ⁨Comment⁩ on ⁨⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:

  It’s… literally the opposite. The giant AI models with trillions of parameters are not something you can run without spending many thousands of dollars, and quantum computers cost millions. These are definitely not services that are going to fall into the hands of everyday people. At best you get small AI models.

• ⁨Comment⁩ on ⁨How we get to 1 nanometer chips and beyond⁩ ⁨⁨4⁩ ⁨months⁩ ago⁩:

  The reason quantum computers are theoretically faster is because of the non-separable nature of quantum systems.

  Imagine you have a classical computer where some logic gates flip bits randomly, and multi-bit logic gates could flip them randomly but in a correlated way. These kinds of computers exist and are called probabilistic computers and you can represent all the bits using a vector and the logic gates with matrices called stochastic matrices.

  The vector necessarily is non-separable, meaning, you cannot get the right predictions if you describe the statistics of the computer with a vector assigned to each p-bit separately, but must assign a single vector to all p-bits taken together. This is because the statistics can become correlated with each other, i.e. the statistics of one p-bit depends upon another, and thus if you describe them using separate matrices you will lose information about the correlations between the p-bits.

  The p-bit vector grows in complexity exponentially as you add more p-bits to the system (complexity = 2^N where N is the number of p-bits), even though the total states of all the p-bits only grows linearly (complexity = 2N). The reason for this is purely an epistemic one. The physical system only grows in complexity linearly, but because we are ignorant of the actual state of the system (2N), we have to consider all possible configurations of the system (2^N).

  The exponential complexity arises from considering what physicists call an “ensemble” of individual systems. We are not considering the state of the physical system as it currently exists right now (which only has a complexity of 2N) precisely because we do not know the values of the p-bits, but we are instead considering a statistical distribution which represents repeating the same experiment an infinite number of times and distributing the results, and in such an ensemble the system would take every possible path and thus the ensemble has far more complexity (2^N).

  This is a classical computer with p-bits. What about a quantum computer with q-bits? It turns out that you can represent all of quantum mechanics simply by allowing probability theory to have negative numbers. If you introduce negative numbers, you get what are called quasi-probabilities, and this is enough to reproduce the logic of quantum mechanics.

  You can imagine that quantum computers consist of q-bits that can be either 0 or 1 and logic gates that randomly flip their states, but rather than representing the q-bit in terms of the probability of being 0 or 1, you can represent the qubit with four numbers, the first two associated with its probability of being 0 and the second two associated with its probability of being 1. Like normal probability theory, the numbers have to all add up to 1, being 100%, but because you have two numbers assigned to each state, you can have some quasi-probabilities be negative while the whole thing still adds up to 100%.

  Indeed, with that simple modification, the rest of the theory just becomes normal probability theory, and you can do everything you would normally do in normal classical probability theory, such as build probability trees and whatever to predict the behavior of the system.

  However, this is where it gets interesting.

  As we said before, the exponential complexity of classical probability is assumed to merely something epistemic because we are considering an ensemble of systems, even though the physical system in reality only has linear complexity. Yet, it is possible to prove that the exponential complexity of a quasi-probabilistic system cannot be treated as epistemic. There is no classical system with linear complexity where an ensemble of that system will give you quasi-probabilistic behavior.

  As you add more q-bits to a quantum computer, its complexity grows exponentially in a way that is irreducible to linear complexity. In order for a classical computer to keep up, every time an additional q-bit is added, if you want to simulate it on a classical computer, you have to increase the number of bits in a way that grows exponentially. Even after 300 q-bits, that means the complexity would be 2^N = 2^300, which means the number of bits you would need to simulate it would exceed the number of atoms in the observable universe.

  In practice, this increase in complexity does not mean you can always solve problems faster. The system might be more complex, but it requires clever algorithms to figure out how to actually translate that into problem solving, and currently there are only a handful of known algorithms you can significantly speed up with quantum computers.

  For reference: arxiv.org/abs/0711.4770