Perspectives on the Quantum State

There are two main styles of interpreting the quantum state: either focusing on the fundamentality of the quantum state (a state or wavefunction realist view), or on how projection operators represent observable properties (an observable-first approach). Rather than being incompatible, I argue that these correspond to taking a 3rd person and 1st person perspective respectively. I further contend that the 1st person perspective - and the observable-first approach that goes with it - is better suited to explain measurement, based on the way that the metrology literature characterises measurement through the quantifiable properties of a system. Finally, I show how the 1st person, observable-first approach can emerge in the world through the process of decoherence, hence showing the compatibility of the two approaches and resolving the need to choose absolutely between them.