This divulgation article by Prof. Brukner talks about the possibility of creating a situation where
"A causing B" and "B causing A" which we call a quantum switch. Such a setup is similar to some predator–prey relationships, in which predator numbers influence prey numbers, yet prey numbers also influence predator numbers. Following work that Ognyan Oreshkov, Fabio Costa, and I published in 2012, we now know that the quantum switch is just one example of an indefinite causal structure, in which it is not defined whether event A is a cause or an effect of event B, or whether the two are independent.
The work link leads to a paper that explains with great detail how to achieve that, and it also includes some applications, like to prove that two no-signalling channels that are not perfectly distinguishable in any ordinary quantum circuit can become perfectly distinguishable through the quantum superposition of circuits with different causal structures
I am a regular programmer without a background in quantum computing and don't quite understand the implications of such articles. What I get, and find very exciting is the possibility of having such expanded causality models as a tool. My question is: how/where could quantum switch fit in the classical computing landscape? Be it low-level hardware design or the (surely upcoming)
else-then-if software pattern