Hidden variable theories

Definition

Hidden variable theories are theoretical frameworks in quantum mechanics that propose the existence of unobservable parameters, or 'hidden variables,' that determine the outcomes of quantum events. These theories aim to provide a deterministic account of quantum phenomena, which contrasts with the inherent randomness found in standard quantum mechanics. By suggesting that particles have properties determined by these hidden variables, proponents believe that a more complete understanding of quantum mechanics can be achieved.

5 Must Know Facts For Your Next Test

1. Hidden variable theories emerged as an attempt to explain the apparent randomness in quantum mechanics by suggesting underlying deterministic factors.
2. Einstein famously supported hidden variable theories, believing they could restore a sense of realism to quantum mechanics, famously remarking that 'God does not play dice.'
3. Bell's theorem demonstrated that any local hidden variable theory must violate certain statistical predictions, leading to the rejection of many hidden variable models.
4. Non-local hidden variable theories, such as de Broglie-Bohm theory, still exist and allow for instantaneous effects across distances, maintaining some deterministic aspects.
5. Experiments designed to test Bell's theorem have overwhelmingly favored predictions from quantum mechanics over hidden variable theories, suggesting that these hidden variables may not exist.

Review Questions

• How do hidden variable theories attempt to explain the randomness observed in quantum mechanics?
  • Hidden variable theories propose that the apparent randomness in quantum outcomes arises from unobservable parameters that influence particle behavior. By introducing these hidden variables, theorists believe they can provide a deterministic framework where outcomes are not truly random but rather determined by these underlying factors. This perspective contrasts sharply with the standard interpretation of quantum mechanics, which accepts inherent randomness as a fundamental characteristic.
• What implications does Bell's theorem have on the validity of local hidden variable theories in relation to quantum entanglement?
  • Bell's theorem shows that local hidden variable theories cannot reproduce all the predictions made by quantum mechanics, especially regarding entangled particles. This result implies that if local realism holds true—meaning no instantaneous influences at a distance—then the correlations predicted by quantum mechanics would be impossible. Therefore, the experimental validation of Bell's inequalities suggests that either locality or realism must be abandoned, fundamentally challenging our understanding of reality and supporting non-local interpretations.
• Evaluate how hidden variable theories interact with modern experimental results in quantum mechanics and what this suggests about our understanding of reality.
  • Modern experiments testing Bell's theorem consistently show results that align with quantum mechanical predictions rather than those from local hidden variable theories. This persistent discrepancy suggests that the classical notions of locality and realism may need reevaluation in light of quantum phenomena. As these experiments continue to reinforce non-local correlations, it implies that our understanding of reality is more complex than previously thought, potentially leading to new interpretations or frameworks in quantum theory that accommodate these findings.

Related terms

Quantum entanglement: A phenomenon in quantum mechanics where two or more particles become correlated in such a way that the state of one particle instantaneously influences the state of another, regardless of distance.

Bell's theorem: A fundamental result in quantum physics that shows no local hidden variable theory can reproduce all the predictions of quantum mechanics, thereby challenging classical intuitions about reality.

Local realism: The philosophical viewpoint that physical processes occurring at one location should not be instantly influenced by events at another distant location, aligning with classical physics principles.