Quantum states: Are they the real thing? (joint colloquium with the Department of Physics and Astronomy) - Terry Rudolph

What is the quantum state? There is no widely agreed answer to this question, despite the ubiquitous and crucial role this mathematical object plays in our lives. Two broad schools of thought can be identified. The \"ontic view\" is that the quantum state describes (partially or completely) the real physical state of affairs. The \"epistemic view\" is that it instead represents some agent\'s knowledge or information about the physical system in question.\r\n \r\nAlthough there are many compelling reasons to favour the epistemic view, I will show that only the ontic view is compatible with three notions seemingly indispensible to science: (i) the existence of systems with physical properties (ii) the idea that measurements respond to, and reveal aspects of, those properties and (iii) the ability to perform independent experiments.\r\n \r\nThis result will hopefully leave you as uncomfortable about the status of the quantum state as I am, and perhaps, like me, after the talk you will find yourself requiring some fortification before having the courage to step out into reality... \r\n