Quantum Darwinism reminds me of one part of the Copenhagen catechism, the idea that the quantum-to-classical transition (as we now call it) somehow revolves around “irreversible amplification” of microscopic to macroscopic properties. In quantum Darwinism, the claim instead is that properties become objectively present when multiple observers could agree on them. As https://arxiv.org/abs/1803.08936 points out on its first page, this is more like “inter-subjectivity” than objectivity, and there are also edge cases where the technical criterion simply fails. Like every other interpretation, quantum Darwinism has not resolved the ontological mysteries of quantum theory.
As for this Natural Latents research program, it seems to be studying the compressed representations of the world that brains and AIs form, and looking for what philosophers call “natural kinds”, in the form of compressions and categorizations that a diverse variety of learning systems would naturally make.
The authors of the article express their personal viewpoint on the definition of subjectivity.
The definition of what it means to be objective in-and-of-itself is up for debate (this definition can be thought of as inter-subjectivity rather than objectivity per se), but that debate is not purpose of this Letter.
I can also agree that a specially prepared environment, for example one consisting of a wall of entangled qubits, does not ensure objectivity, since it simply continues the chain of superpositions: atom, Geiger counter, vial, cat, wall in the thought experiment. But our world is arranged such that this situation does not occur, at least without deliberate intervention by an experimenter.
I tried to imagine such a thought experiment — it is possible with a qubit, but not with a cat. In fact, this would mean creating a long-lived quantum memory, which I do not rule out. Does this negate objectivity?
I would like to note that a pointer state is the state of a pointer of a measuring device—this is where the name comes from. For example, in the case of Schrödinger’s cat, one can construct a device that indicates whether the cat is alive or dead, thereby ensuring objectivity even in the absence of a human observer.
Moreover, such devices can rely on different measurable signals: an electroencephalogram, a cardiogram, the cat’s heat production, the amount of CO₂ it exhales, and so on. A classical device that would display a superposition of the states ⟨alive⟩ + ⟨dead⟩ cannot be constructed; therefore, such a superposition is not a pointer state. Human sensory organs are themselves such devices, as is the environment surrounding the cat: EEG and ECG signals generate electromagnetic radiation in the environment, heat production raises its temperature, and CO₂ emission increases the ambient CO₂ concentration.
The mere existence of such “devices” already makes pointer states objective, because any number of observers can look at the pointers!
Can good and evil be pointer states? And if they can, then this would be an objective characteristic, understood in the same way by both humans and AI and the alignment problem is already solved!
Here one has to be very careful with the proof of such a multiverse picture, because, as usual, we replace the observed averaging of outcomes of experiments repeated in time in our world by the squared modulus of the (normalized) amplitude interpreted as the probability of our world which effectively means averaging over an ensemble of parallel worlds, whose number since the birth of the universe may be infinite.
The explanatory idea is there, but even in the 2025 paper it still looks underdeveloped. I don’t understand this very well, so I can’t give more details.
Quantum Darwinism reminds me of one part of the Copenhagen catechism, the idea that the quantum-to-classical transition (as we now call it) somehow revolves around “irreversible amplification” of microscopic to macroscopic properties. In quantum Darwinism, the claim instead is that properties become objectively present when multiple observers could agree on them. As https://arxiv.org/abs/1803.08936 points out on its first page, this is more like “inter-subjectivity” than objectivity, and there are also edge cases where the technical criterion simply fails. Like every other interpretation, quantum Darwinism has not resolved the ontological mysteries of quantum theory.
As for this Natural Latents research program, it seems to be studying the compressed representations of the world that brains and AIs form, and looking for what philosophers call “natural kinds”, in the form of compressions and categorizations that a diverse variety of learning systems would naturally make.
The authors of the article express their personal viewpoint on the definition of subjectivity.
I can also agree that a specially prepared environment, for example one consisting of a wall of entangled qubits, does not ensure objectivity, since it simply continues the chain of superpositions: atom, Geiger counter, vial, cat, wall in the thought experiment. But our world is arranged such that this situation does not occur, at least without deliberate intervention by an experimenter.
I tried to imagine such a thought experiment — it is possible with a qubit, but not with a cat. In fact, this would mean creating a long-lived quantum memory, which I do not rule out. Does this negate objectivity?
I would like to note that a pointer state is the state of a pointer of a measuring device—this is where the name comes from. For example, in the case of Schrödinger’s cat, one can construct a device that indicates whether the cat is alive or dead, thereby ensuring objectivity even in the absence of a human observer.
Moreover, such devices can rely on different measurable signals: an electroencephalogram, a cardiogram, the cat’s heat production, the amount of CO₂ it exhales, and so on. A classical device that would display a superposition of the states ⟨alive⟩ + ⟨dead⟩ cannot be constructed; therefore, such a superposition is not a pointer state. Human sensory organs are themselves such devices, as is the environment surrounding the cat: EEG and ECG signals generate electromagnetic radiation in the environment, heat production raises its temperature, and CO₂ emission increases the ambient CO₂ concentration.
The mere existence of such “devices” already makes pointer states objective, because any number of observers can look at the pointers!
Can good and evil be pointer states? And if they can, then this would be an objective characteristic, understood in the same way by both humans and AI and the alignment problem is already solved!
If you only have unitary evolution, you end up with superpositions of the form
|system state 1> |pointer state 1> + |systems state 2> |pointer state 2> + … + small cross-terms
Are you proposing that we ignore all but one branch of this superposition?
My favorite point origins of Born’s rule of view is the following. The final state is a superposition, but we are all inside it.
And since these two states are orthogonal, state 1⟩ does not see 2⟩, and vice versa; God only knows.
The works by Zurek (https://arxiv.org/pdf/1807.02092) and the more recent one (https://arxiv.org/html/2209.08621v6) shed more light on this.
Here one has to be very careful with the proof of such a multiverse picture, because, as usual, we replace the observed averaging of outcomes of experiments repeated in time in our world by the squared modulus of the (normalized) amplitude interpreted as the probability of our world which effectively means averaging over an ensemble of parallel worlds, whose number since the birth of the universe may be infinite.
The explanatory idea is there, but even in the 2025 paper it still looks underdeveloped. I don’t understand this very well, so I can’t give more details.
This would appear to be just saying that if we can build a classical detector of good and evil, good and evil are objective in the classical sense.