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| Format: | Preprint |
| Published: |
2025
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| Online Access: | https://arxiv.org/abs/2509.01290 |
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| _version_ | 1866911132207284224 |
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| author | von Liechtenstein, Maximilian Ralph Peter |
| author_facet | von Liechtenstein, Maximilian Ralph Peter |
| contents | We introduce a new paradox, which we call Counterfactual Local Friendliness (CLF): a Wigner's-friend-type logical collision in which every decisive inference is obtained by interaction-free flags whose disturbance on the probed object is bounded by a tunable parameter $ε$. Under (Q) universal unitarity for outside observers, (S) single-outcome facts, (C) cross-agent consistency, and (IF-$ε$) $ε$-counterfactuality of the friends' internal modules, quantum theory predicts a nonzero post-selected event that forces mutually incompatible certainties about a single upstream variable -- without appealing to absorptive or projective in-lab measurements.
We also derive an $ε$-IF three-box noncontextual bound: any single-world, noncontextual model satisfying exclusivity and epsilon-stability must obey $P(A) + P(B) \le 1 + K_ε$, while quantum theory yields $P(A) = P(B) = 1$, violating the bound for arbitrarily small $ε$. Together these results isolate what is paradoxical about counterfactual phenomena: not energy exchange with the probed system, but the incompatibility of agent-level facts in single-world narratives. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_01290 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Counterfactual Local Friendliness: An epsilon-Bounded Interaction-Free Paradox and a Disturbance-Robust Three-Box Inequality von Liechtenstein, Maximilian Ralph Peter Quantum Physics We introduce a new paradox, which we call Counterfactual Local Friendliness (CLF): a Wigner's-friend-type logical collision in which every decisive inference is obtained by interaction-free flags whose disturbance on the probed object is bounded by a tunable parameter $ε$. Under (Q) universal unitarity for outside observers, (S) single-outcome facts, (C) cross-agent consistency, and (IF-$ε$) $ε$-counterfactuality of the friends' internal modules, quantum theory predicts a nonzero post-selected event that forces mutually incompatible certainties about a single upstream variable -- without appealing to absorptive or projective in-lab measurements. We also derive an $ε$-IF three-box noncontextual bound: any single-world, noncontextual model satisfying exclusivity and epsilon-stability must obey $P(A) + P(B) \le 1 + K_ε$, while quantum theory yields $P(A) = P(B) = 1$, violating the bound for arbitrarily small $ε$. Together these results isolate what is paradoxical about counterfactual phenomena: not energy exchange with the probed system, but the incompatibility of agent-level facts in single-world narratives. |
| title | Counterfactual Local Friendliness: An epsilon-Bounded Interaction-Free Paradox and a Disturbance-Robust Three-Box Inequality |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2509.01290 |