HY4041 PHILOSOPHY OF QUANTUM MECHANICS

Feynman famously wrote that 'I think I can safely say that nobody understands quantum mechanics. ... Do not keep saying to yourself, if you can possibly avoid it, `But how can it be like that?' because you will get `down the drain', into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.' But that seems like a perfect question for philosophers -- and some physicists -- who want to know what quantum mechanics is (or isn't) telling us about the world: how can it be like that? For instance, is Schrodinger's cat really 'dead and alive'? And what does it mean for it to 'become' dead or alive when we 'observe' it? To tackle this question, we will study the foundations of quantum mechanics. We start by understanding the 'bare formalism' of quantum mechanics at a conceptual and logical level, and the crucial experiments in support of this formalism over the classical picture. We then consider three questions at the core of this formalism: the measurement problem, the Einstein-Podolsky-Rosen argument for non-locality, and Bell's theorem. We will then study 'the standard picture' to quantum mechanics: the so-called Copenhagen interpretation, and an emphasis on measurement and instrumentalism, diagnosing some conceptual worries with this picture. We then turn to three robust families of proposals for approaching quantum mechanics and its ontology: the Ghirardi-Rimini-Weber (GRW) theory, Bohmian mechanics, and the many-worlds interpretation. In so doing, we engage with philosophical questions about locality, determinism, the dimensionality of fundamental space, underdetermination of theory by data, scientific realism, the arrow of time, the meaning of quantum probabilities, among others. There is no formal prerequisite for the course, though a high school or undergraduate background in physics will be helpful. A tolerance for math is important, however, as we'll dive into physics. Every effort will be made to present the math and physics as cleanly and accessibly as possible. Students without technical backgrounds can and do thrive in this course, so long as math anxiety is left behind.