The role of complex numbers in quantum physics

The standard formulation of quantum mechanics relies on complex numbers, which include an imaginary part. Physicists have wondered whether this can be considered a form of mathematical convenience, just as complex numbers facilitate calculations in electromagnetism, or not. Marc-Oliver Renou and colleagues now construct a Bell-like inequality which allows the experimental discrimination between predictions of standard quantum physics and of a version of quantum physics that is entirely built without complex numbers. Their result suggests that it is only in multi-party scenarios that such differences become noticeable.