Perceived contradiction in non-locality principle

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SUMMARY

This discussion centers on the perceived contradiction in the non-locality principle as it relates to polarization-entangled photons A and B measured by Alice and Bob. The key point is that while there is a correlation between the measurements of the two photons, the actual polarization states are not defined until measurement occurs. The conversation highlights that the measurement of one photon does not determine the state of the other, and relativity does not influence the causal relationship between the measurements. Ultimately, the discussion emphasizes that the wave function collapse occurs upon interaction with a macroscopic object, such as a polarizing filter, rather than being a direct result of one photon influencing the other.

PREREQUISITES
  • Understanding of quantum entanglement and polarization states
  • Familiarity with wave function collapse in quantum mechanics
  • Knowledge of measurement theory in quantum mechanics
  • Basic principles of special relativity and its implications for causality
NEXT STEPS
  • Explore the implications of Bell's theorem on quantum entanglement
  • Study the concept of wave function collapse in various interpretations of quantum mechanics
  • Investigate the role of macroscopic objects in quantum measurements
  • Learn about the experimental setups involving birefringent crystals and their effects on photon polarization
USEFUL FOR

This discussion is beneficial for physicists, quantum mechanics students, and anyone interested in the foundational aspects of quantum theory, particularly those exploring the intersection of entanglement, measurement, and relativity.

  • #61
.Scott said:
That lack of time-based cause and effect is the core reason for taking the entire measurement process as one fully-integrated event.
Lets say you measure one particle from entangled pair and then depending from the measurement result you decide to perform or not perform entanglement swapping of second particle with a particle from another entangled pair.
Can you take it as one fully-integrated event?
 
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  • #62
zonde said:
Lets say you measure one particle from entangled pair and then depending from the measurement result you decide to perform or not perform entanglement swapping of second particle with a particle from another entangled pair.
Can you take it as one fully-integrated event?
Well, you can. But that makes things too easy. Normally you want to keep one measurement from having an obvious influence on the other so that there is no "hidden value" solution.
Perhaps more importantly, the measurement of just one particle is "random", he equivalent of a coin flip. It is only when you have a population of A measurements to compare to a corresponding population of B measurements that you see a pattern.
 

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