>[!abstract] >In quantum mechanics, **superdeterminism** is the idea that the behavior of a quantum particle and the choice of its measurement are both pre-determined, so that the former necessarily depends on the latter. > >More generally, superdeterminism posits that all events (including one's choices) are determined by the initial conditions of the universe, which were set at the Big Bang (or whatever came at the start of the universe). >[!example] Example: the double-slit experiment >In a superdeterministic interpretation of the double-slit experiment, the photon's path **and** the measurement type (at the screen, in which case an interference pattern appears, or at one of the slits, in which case the pattern does not appear) are both pre-determined. There is, then, no need for a faster-than-light collapse of the wave function between the two slits. >[!question] How does superdeterminism relate to quantum mechanics? >Superdeterminism is an assumption of the [[Quantum mechanics, cellular automaton interpretation|cellular automaton interpretation of quantum mechanics]], in which it serves to explain how the measurement of entangled particles can be done at any distance between them without invoking faster-than-light communication (spooky action at a distance). If the state of the entangled particles and the fact that they will be measured are both pre-determined, then by necessity, the measurement will always confirm the entanglement. The particles do not "agree" on their property (e.g., spin) at the time of measurement; they always had that property because it was always determined that they would be measured. >[!question] How does superdeterminism relate to Bell's theorem? >Superdeterminism rejects one of the three assumptions of Bell’s theorem, which is **statistical independence**, the idea that one's experimental choices are truly free, and not secretly rigged by the same universal script that controls the particles. >[!question] Is superdeterminism compatible with free will? >Superdeterminism is **incompatible** with libertarian free will (the classical idea that we can always choose otherwise, even if everything else remains the same). It is, on the other hand, **compatible** with [[compatibilism|compatibilistic free will]] in which one's choices are still determined, but by one's brain, past, character, etc. rather than by randomness. >[!question] How is superdeterminism different from plain determinism? >**Determinism** is the idea that all physical processes are direct consequences of physical laws that leave nothing to randomness. **Superdeterminism** is functionally equivalent, but explicitly "emphasizes that the observers themselves behave in accordance with the same laws" ([[t' Hooft, 2016|t' Hooft, 2016, p. 112]]). >[!references] References >- [[Hossenfelder, 2021|Hossenfelder (2021)]]: A lay deeper dive into superdeterminism and its implications. >- [[Hossenfelder, 2025b|Hossenfelder (2025b)]]: A lay overview of the [[Quantum mechanics, cellular automaton interpretation|cellular automation intepretation of quantum mechanics]] which depends on superdeterminism. >- [[O'Dowd, 2022]]: A video introduction to superdeterminism. >- [[t' Hooft, 2016|t' Hooft (2016)]]: >[!related] >- **North** (upstream): — >- **West** (similar): — >- **East** (different): — >- **South** (downstream): —