Wigner’s Friend: A Quantum Mystery
Quantum mechanics is weird. Wigner’s Friend thought experiment shows this.
The Thought Experiment
Eugene Wigner proposed it. Imagine a friend in a lab. She measures a quantum particle. The particle is in a superposition.
The Paradox
Wigner’s friend observes the particle. The particle collapses to one state. But Wigner outside the lab doesn’t know the result. To him, the particle is still in a superposition.
The Problem
When does the particle’s state collapse? Is it when the friend observes or when Wigner knows?
Implications
- Reality depends on observation. Or does it?
- Quantum mechanics might not be objective.
Interpretations
- Copenhagen interpretation: collapse happens upon observation.
- Many-worlds interpretation: all outcomes exist.
Conclusion
Wigner’s Friend challenges our understanding. Quantum mechanics remains mysterious. The nature of reality is still debated.