+- Scivillage.com Casual Discussion Science Forum (https://www.scivillage.com)
+-- Forum: Science (https://www.scivillage.com/forum-61.html)
+--- Forum: Chemistry, Physics & Mathematics (https://www.scivillage.com/forum-77.html)
+--- Thread: Article The most important quantum advance of the 21st century (/thread-19728.html)
The most important quantum advance of the 21st century - C C - Feb 4, 2026
https://bigthink.com/starts-with-a-bang/most-important-quantum-advance-21st-century/
EXCERPTS: You can calculate the probability of a set of outcomes, but quantum physics gives us no way to determine what the outcome of any one particular quantum system will actually be, no matter how much you know about it. This fact about the Universe has spawned much outrage among physicists and philosophers alike since it was first noticed, which in turn has led to many proposed scenarios to attempt to resolve the feeling of discomfort that we feel when we encounter and ponder these properties.
[...] At the core of the argument is whether quantum states are “ontic” or “epistemic” in nature. These aren’t common terms that people use (even most physicists rarely use them), with the difference being as follows.
- For ontic quantum states, those states would correspond directly to states of reality, with no room for additional knowledge about reality existing in some hidden, but unknown to humans, set of information-carrying variables.
- Meanwhile, for epistemic quantum states, those states may correspond only to probabilistic states of knowledge about reality, but those states are allowed to be incomplete, where additional knowledge could exist in some type of hidden, information carrying variables.
[...] What’s remarkable about this theorem is that it relies solely on three base assumptions made by the authors [...] If any of these assumptions are violated or invalidated, then there’s still wiggle room to argue that the quantum state is not a real object, or that quantum systems don’t have any physical properties at all.
However, if all three of these assumptions are accepted, then the epistemic interpretation of reality is ruled out, leaving us with no alternative but to accept the “weirdness” of quantum mechanics as inherent to, and fundamental to, the nature of reality. That truly is profound, and why the PBR theorem stands tall as the most important development in quantum foundations of the 21st century so far! (MORE - missig details)
RE: The most important quantum advance of the 21st century - Syne - Feb 4, 2026
1. That if an isolated (non-entangled) quantum system can be prepared with a pure state, there will be a well-defined set of physical properties resulting from that preparation.
2. That multiple quantum systems can be independently prepared such that their physical properties are uncorrelated with one another.
3. And that measuring apparatuses respond solely to the physical properties of the systems that they are measuring, whether or not those properties are well-determined or obey a probability distribution.
It would seem odd to assume that our measuring equipment could respond to information about a system that is not an inherent, physical property of the system. That would seem to require us postulating hidden variables without significant, or even adequate, justification.
In conclusion, we have presented a no-go theorem, which—modulo assumptions—shows that models in which the quantum state is interpreted as mere information about an objective physical state of a system cannot reproduce the predictions of quantum theory. The result is in the same spirit as Bell’s theorem, which states that no local theory can reproduce the predictions of quantum theory.
- https://en.wikipedia.org/wiki/Pusey%E2%80%93Barrett%E2%80%93Rudolph_theorem