Hidden variables

Definition

Hidden variables are theoretical parameters that are not directly observable but are believed to influence the behavior of quantum systems. In the context of quantum mechanics, especially concerning quantum entanglement and Bell's theorem, hidden variables serve as potential explanations for the seemingly non-local correlations observed in entangled particles. The idea is that these hidden variables could provide a deterministic framework to account for the randomness inherent in quantum mechanics.

5 Must Know Facts For Your Next Test

1. Hidden variable theories aim to restore determinism to quantum mechanics by suggesting that unobserved factors influence quantum outcomes.
2. Bell's theorem shows that no local hidden variable theory can reproduce all predictions of quantum mechanics, particularly in experiments involving entangled particles.
3. The existence of hidden variables would imply a level of realism in quantum mechanics that is at odds with the standard interpretation, which embraces inherent randomness.
4. Experiments testing Bell's theorem have consistently shown violations of Bell inequalities, suggesting that hidden variable models cannot fully describe quantum phenomena.
5. The debate over hidden variables continues to be a central issue in understanding the foundations of quantum mechanics and its interpretation.

Review Questions

• How do hidden variable theories attempt to address the apparent randomness observed in quantum mechanics?
  • Hidden variable theories propose that underlying, unobserved factors influence the outcomes of quantum events, thereby introducing a level of determinism. By suggesting that particles have specific properties determined by these hidden variables before measurement, proponents believe they can explain the seemingly random behavior seen in experiments. This perspective challenges the traditional view of inherent randomness in quantum mechanics and seeks to establish a more classical framework.
• Discuss how Bell's theorem challenges the viability of local hidden variable theories in explaining quantum entanglement.
  • Bell's theorem presents a significant challenge to local hidden variable theories by demonstrating that they cannot reproduce all predictions of quantum mechanics, especially regarding entangled particles. It establishes a set of inequalities, known as Bell inequalities, which local theories must satisfy. However, experiments consistently violate these inequalities, indicating that either locality or realism must be abandoned if one adheres to a hidden variable model. This has profound implications for our understanding of reality in the quantum realm.
• Evaluate the impact of experimental violations of Bell inequalities on the discussion surrounding hidden variables and their role in quantum mechanics.
  • The experimental violations of Bell inequalities have had a transformative impact on the debate over hidden variables, casting doubt on their viability as explanations for quantum phenomena. These results suggest that any potential hidden variables cannot operate under local realism, thus challenging the notion that classical intuitions about causality and separability apply at the quantum level. As researchers explore interpretations like many-worlds or pilot-wave theory, these findings prompt a reevaluation of what we consider 'real' in the context of quantum mechanics and whether determinism can ever truly reconcile with its probabilistic nature.

Related terms

Quantum Entanglement:

A phenomenon where two or more particles become linked, such that the state of one particle instantly influences the state of another, regardless of the distance separating them.

Bell's Theorem: A fundamental result in quantum mechanics that demonstrates the impossibility of local hidden variable theories to explain the correlations predicted by quantum mechanics.

Local Realism: The philosophical viewpoint that physical processes occurring at one location cannot instantly influence those at another location, supporting the idea of causality and the existence of hidden variables.