Thought Experiment Index
A thought experiment isolates a conceptual tension by specifying ideal preparations, interventions, and reasoning rules. It need not be a feasible laboratory experiment in its original form. This index identifies the target of each argument and links to the canonical treatment.
States, locality, and outcomes
Section titled “States, locality, and outcomes”| Scenario | Question isolated | Essential caution | Explanation |
|---|---|---|---|
| EPR | Can locality and perfect predictions motivate an incompleteness argument? | The historical argument is not identical to a later Bell inequality | EPR Argument |
| Schrödinger’s cat | What happens when microscopic alternatives correlate with macroscopic records? | The point is an unresolved description of outcomes, not evidence for conscious collapse | Schrödinger’s Cat |
| GHZ | Can perfect multipartite correlations contradict predetermined local values? | Noise turns ideal all-or-nothing constraints into statistical tests | GHZ Argument |
| Hardy | Can a positive-probability event conflict with local explanations given other zero probabilities? | Ideal zero probabilities require careful treatment in finite data | Hardy Paradox |
Agents and conditional descriptions
Section titled “Agents and conditional descriptions”Wigner’s friend. The friend assigns a definite internal record while Wigner may assign a coherent state to the larger laboratory. The challenge concerns how descriptions and facts are related. It does not by itself require consciousness to change dynamics. See Wigner’s Friend.
Frauchiger–Renner. Several agents combine quantum predictions and certainty claims under a specified consistency package. The tension concerns that package; it is not a demonstration that the quantum probability calculus is internally contradictory in every application. See Frauchiger–Renner Argument.
Delayed choice. A later choice selects which measurement is performed on a quantum system. It need not imply that a later act changes an earlier recorded outcome. See Delayed-Choice Experiments.
Quantum eraser. Conditioning on an auxiliary measurement sorts data into subsets with different interference patterns. The unconditioned distribution still obeys no-signaling. See Quantum Eraser.
Information and thermodynamics
Section titled “Information and thermodynamics”Quantum Maxwell-demon variants. Measurement records and feedback can change the work obtainable from a system. A complete cycle must account for memory and resource consumption. The canonical treatment is Maxwell’s Demon and Information, with Landauer’s Principle for erasure.
These scenarios concern information-bearing physical systems. Replacing a memory by a human observer does not add a new thermodynamic law.
A reliable reading procedure
Section titled “A reliable reading procedure”Write down the state, the measurement order, the conditional information available to each agent, and the claims being combined. Mark counterfactual statements separately from outcomes in the same run.
Then ask whether the tension arises from a physical prediction, an assumption about unperformed measurements, or a rule for combining descriptions. The answer determines what a laboratory implementation could test.
The experiment index distinguishes realizable tests from their idealized conceptual ancestors.
References
Section titled “References”- Einstein, Albert, Boris Podolsky, and Nathan Rosen, “Can quantum-mechanical description of physical reality be considered complete?” Physical Review 47, 777–780 (1935). Paper.
- Frauchiger, Daniela, and Renato Renner, “Quantum theory cannot consistently describe the use of itself,” Nature Communications 9, 3711 (2018). Paper.
- Scully, Marlan O., and Kai Drühl, “Quantum eraser: A proposed photon correlation experiment concerning observation and ‘delayed choice’ in quantum mechanics,” Physical Review A 25, 2208–2213 (1982). Paper.