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Despite this empirical success, there remains ongoing debate about how quantum mechanics should be understood as a description of the physical world. The question is, how does the mathematical formalism relate to experienced reality? In particular, it is unclear what, if anything, the theory tells us about the physical systems independent of measurement occurring.

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In quantum mechanics, the state, i.e. location, energy, or spin, of a system is represented using a mathematical statement Ψ that can be written as a sum of several terms, where each term is associated with a different possible physical outcome.

Interpreted straightforwardly, it appears to describe systems as occupying multiple, mutually exclusive states at the same time, similar to how a wave occupies many locations at once.

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​​​​However, when a measurement is performed, only a single outcome is ever observed.

 

One position, one spin value, or one energy level is recorded, while the other possibilities do not appear in the result. The theory itself does not specify how or why this transition from multiple possibilities to a single outcome occurs, nor does it identify any physical feature of the measurement process that would naturally select one result over the others. This mismatch between the mathematical description and observed outcomes is commonly referred to as the measurement problem.

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An interpretation of quantum mechanics is an attempt to clarify how the theory's formalism should be understood in relation to physical reality. Simply put, what is going on?! Some interpretations modify the theory to restore determinism or realism; others embrace indeterminacy or non-locality; still others argue that no underlying physical story is required at all. These competing views differ on fundamental questions:

 

Is the universe deterministic or probabilistic?

Is reality local or non-local?

What, if anything, is truly “real”?

And what exactly happens during a measurement?

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Each interpretation tells its own story about the world: its ontology, its rules, its hidden mechanisms, or lack thereof. In this sense, interpretations are not unlike movies: distinct narratives built around the same script. These different narratives built around a shared mathematical structure can emphasise different assumptions and resolve the same conceptual difficulties in different ways.

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This Website:

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QIDb is designed to help students and interested readers explore quantum mechanics through its many competing interpretations. Each interpretation is presented as a distinct entry: a 'movie'. It includes a trailer, a clear conceptual outline, a historical context, and points of comparison. Users can examine and compare interpretations across criteria such as explanatory scope, ontological commitments, locality, determinism, and conceptual clarity.

 

Welcome to QIDb, the Quantum Interpretations Database.