Cartoon Quantum Spacetime

By Maria Violaris

When Dr Stefano Gogioso began to explain quantum operations in spacetime, it wasn't with streams of mathematical equations - it was with drawings. A combination of boxes and wires connected together can be used to compute fundamental quantum results by following rules about how to manipulate these diagrams. Each box is a quantum process, and the wires are inputs and outputs, which can be quantum or classical.

Discrete events in spacetime can be mapped on to a network of these boxes and wires. But things start to get weirder when indefinite causality enters the picture. Certain combinations of these boxes do not have a set "causal order" - either one of two processes could have happened first. Dr Gogioso presented a quantum spacetime-bending (and mind-bending) scenario where there is a superposition of event A causing event B, and event B causing event A. He led us through a range of pictures to show exactly what this means for quantum theory and causation.

A final question remains: did this talk cause our society members to be curious about the peculiar nature of quantum spacetime, or did the curiosity of our society members about the peculiar nature of quantum spacetime cause the talk? With the indefinite causality of quantum spacetime, perhaps it was both at once.