Matthew F. Pusey

On the reality of the quantum state

A no-go theorem on the reality of the quantum state is demonstrated. If the quantum state merely represents information about the physical state of a system, then predictions that contradict those of quantum theory are obtained.

Stabilizer Notation for Spekkens’ Toy Theory

Spekkens has introduced a toy theory (Spekkens in Phys. Rev. A 75(3):032110, 2007) in order to argue for an epistemic view of quantum states. I describe a notation for the theory (excluding certain joint measurements) which makes its similarities and differences with the quantum mechanics of stabilizer states clear. Given an application of the qubit stabilizer formalism, it is often entirely straightforward to construct an analogous application of the notation to the toy theory. This assists calculations within the toy theory, for example of the number of possible states and transformations, and enables superpositions to be defined for composite systems.