Are there any other nondeterministic processes than measurement in quantum theory?

Question

Nondeterministic refers to a system or process that does not have a single predictable outcome. In other words, when a system is nondeterministic, it means that multiple outcomes are possible for a given set of inputs or conditions. Given that it can be associated with randomness.

For physics nondeterministic is the lack of predictability (am I right?). The unpredictability in classical regime (say the motion of classical atoms in a box) is given because of existence of many variables that is hard to keep track of and also the ignorance of the human with regard to the system. The quantum mechanics has nondeterministic behavior only in the measurement process.

My question is that other than the measurement which is nondeterministic (in the sense that the outcome would be randomly distributed over a probability distribution), is there any other process that has such property (in any other regimes such as relativistic)? If yes what and if no, why quantum measurement seems to be special in this case?

Does this answer your question? Is the universe fundamentally deterministic? — Stéphane Rollandin, Jul 15 '23 at 09:56
@StéphaneRollandin Thank you but I don't think that universe is fundamentally deterministic, because I know quantum measurement exists, which is nondeterministic. I am asking whether or not there are other processes that is non deterministic. — Kid A, Jul 15 '23 at 11:13
There are classical movements wich are called chaotic. so you can not predict the development in time. The most known instance is the butterfly moving a wing in Brazil influencing the weather in USA — trula, Jul 15 '23 at 13:44

score 1 · Accepted Answer · answered Jul 18 '23 at 12:37

There are many nondeterministic processes at a macroscopic scale: formation of a rogue wave, start of an avalanche, calving of a glacier, formation of a tornado, Brownian motion, birth of a star…

They are all an avalanche, a self amplificating process starting at the quantum level at a time which is undeterministic: the tiping point ( see Heiseinberg incertitude principle ).

score 0 · Answer 2 · answered Jul 15 '23 at 14:17

Measurement processes are a subset of decoherence processes. Decoherence occurs when there is an irreversible interaction between the quantum system of interest and some other system. That other system may be measurement apparatus, but it doesn't need to be. Decoherence is stochastic, not deterministic.

Are there any other nondeterministic processes than measurement in quantum theory?

2 Answers2