{"id":"cfe9de7e-4249-409e-a52e-48f2f3890a96","arxiv_id":"2507.14672","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":2.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"Extended Wigner's Friend scenarios, under five stated assumptions, contradict the idea that a measurement outcome is an absolute fact shared by all observers.","lead":"This paper explains the Wigner's Friend paradox, where a measurement inside a sealed laboratory is a definite fact for the friend but a superposition for the outside observer. It argues that modern extended versions of the experiment suggest that measurement events are not absolute facts, but exist only relative to each observer.","discovery_kind":"review","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The §4.3 contradiction only shows that at least one of five assumptions fails; since §4.4 concedes that undoing a measurement makes the friend's result no longer a fact, the argument does not single out absoluteness of observed events, so the central claim is not forced.","rationale":"The reader's CONDITIONAL verdict already identifies the same fragile assumption, and I agree that hypothesis 5 is the least secure. My stress-test goes one step further: the paper's own §4.4 is not just a practical difficulty but a logical one. If a measurement can be undone, then the 'observed event' that the friend reported is no longer a fact in the branch where the undo occurs. The no-go theorem requires comparing probabilities across different settings, including settings where the friend's outcome has been undone; without a rule for what 'Charlie's result' means after the undo, equalities 5–7 are not well-defined. This means the contradiction cannot be used to select AOE as the false assumption. The paper's conclusion is conditional on a premise the author himself weakens. However, this is not a fatal flaw: the paper is presented partly as a review, and the abstract uses 'seem to imply.' The reader's recommended conditions—clarify the review status, supply the ConSol derivation, align the title with §4.4—would address the concern. I therefore do not change the verdict; I would keep CONDITIONAL.","tokens_in":11993,"tokens_out":5273,"duration_ms":59698,"concrete_test":"Re-derive the §4.3 argument in a formal probabilistic model where assumption 5 is replaced by its negation: measurements by Charlie and Debbie are irreversible, so Alice and Bob cannot meaningfully choose x=1 or y=1. Define the joint distribution only over runs with x=0,y=0, x=0,y=1, and x=1,y=0, and check whether the equalities 1–3 are consistent with AOE. If a consistent assignment exists that violates no equality, the contradiction is entirely dependent on undoability, and AOE is not ruled out.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's title-level claim that events are not absolute is supported by the §4.3 derivation only if the contradiction compels abandoning AOE. But the derivation is a disjunctive conclusion: hypotheses 1–5 are jointly inconsistent, so the theorem says nothing about which hypothesis is false. The author's own §4.4 reservation directly attacks the fifth hypothesis: 'If Wigner undoes the measurement done by Charlie, it becomes difficult to consider that the result of Charlie's measurement is still a fact.' When Alice chooses x=1, Charlie's outcome c is erased before Alice's outcome a is defined; equally, Bob's y=1 erases d. The equalities 5–7 that produce the chain (a=-)=>(d=1)=>(c=0)=>(b=+) therefore presuppose that c and d are still facts in a run where they have been undone. If one rejects undoability, as an irreversible measurement model would, those probabilities are undefined, the contradiction disappears, and AOE remains viable. The paper does not provide a reason to prefer abandoning AOE over abandoning assumption 5; its own caveat points the other way. Thus the central claim 'events are not absolute' is not established by the argument presented.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This manuscript is a general review of Wigner's-Friend-type thought experiments and their implications. After recapitulating the original scenario and surveying interpretations (Copenhagen, many-worlds, relational QM, objective collapse, QBism, and the author's own Convivial Solipsism), the paper presents a simplified extended-Wigner's-Friend no-go argument based on the Hardy state and five assumptions: locality for observed events, no superdeterminism, universality of quantum mechanics, absoluteness of observed events, and the possibility of undoing a measurement. The argument derives probability equalities that, when combined by locality, yield a contradiction, and the paper concludes that at least one assumption must be abandoned, usually absoluteness of observed events. The final sections discuss implications for realism, quantum information, and the author's Convivial Solipsism interpretation.","tokens_in":12125,"tokens_out":9644,"duration_ms":108273,"significance":"The paper has genuine expository value: it condenses a well-known no-go argument into a compact derivation, and the four probability equalities in §4.3 are elementary and checkable from standard quantum mechanics. The manuscript is also honest in flagging the difficulty of the undo assumption in §4.4. However, the significance as a research contribution is limited by a gap between the no-go result actually proved and the advertised conclusion. The derivation shows that the five assumptions are jointly inconsistent; it does not show that absoluteness of observed events, rather than one of the other assumptions, is false. Since the paper's own caveat about undoing a measurement points toward a natural way to escape the contradiction without abandoning AOE, the central claim that 'events are no longer absolute' is not secured. The paper is best read as an interpretive essay and review rather than a proof of observer-dependent facts.","major_comments":[{"comment":"The locality-based transfer from settings (x=0,y=1) and (x=1,y=0) to the single run (x=1,y=1) presupposes that Charlie's outcome c and Debbie's outcome d are well-defined facts even when Alice and Bob undo the corresponding friend measurements. This is precisely what the paper itself doubts in §4.4: 'If Wigner undoes the measurement done by Charlie, it becomes difficult to consider that the result of Charlie's measurement is still a fact.' Without a supplementary rule specifying whether an undone outcome remains an event, the probabilities p(c=0,b=−|x=1,y=1) and p(a=−,d=0|x=1,y=1) are undefined, and the contradiction chain (a=−)⇒(d=1)⇒(c=0)⇒(b=+) has no well-defined starting point. The derivation therefore does not go through under the assumptions as stated.","section":"§4.3, equalities 5–7"},{"comment":"The argument establishes only that the conjunction of assumptions 1–5 is inconsistent. The statement 'So we have to abandon at least one of them. Usually, it is the absoluteness of observed events (AOE) that is abandoned' reports an interpretive convention; it does not follow from the derivation. Since §4.4 explicitly raises a serious difficulty for assumption 5, rejecting AOE is not the unique or even the most natural resolution. To support the abstract's claim that 'it is no more possible to consider events as absolute', the paper would need either a defense of assumption 5 against the §4.4 objection or an independent argument that singles out AOE.","section":"§4.3, final paragraph"},{"comment":"The paper criticizes Brukner's theorem for relying on 'too strong assumptions (namely to compare results that cannot be obtained in a single experiment)', yet the derivation presented here also combines probability equalities obtained under different settings (equalities 1–4) into statements about a single run (equalities 5–8) using the locality assumption. This move can be legitimate in a Bell-type argument, but the paper applies a stricter standard to Brukner's theorem without explaining why its own use of locality is not vulnerable to the same objection. A precise formulation of 'locality for observed events' — in particular the counterfactual status of outcomes in runs where the measurement is undone — is needed.","section":"§4.3, introduction"}],"minor_comments":[{"comment":"The section numbering is duplicated: '4.3 Experimental Realizations' follows '4.3 Other no-go theorems', and '4.4 A few reservations' should be renumbered accordingly.","section":"§4.3/§4.4"},{"comment":"The abstract says 'no more possible to consider events as absolute', while the conclusion says these results 'suggest' an inherent tension; the paper should commit to a consistent strength of claim, or explicitly frame the conclusion as conditional on accepting all five assumptions.","section":"Abstract and §7"},{"comment":"The equalities 1–4 are described as easy to verify, but no explicit unitary operators for the friends' measurements or for the undo operations are provided; at least a brief derivation or a table of the relevant states would make the argument reproducible.","section":"§4.3"},{"comment":"There are numerous typos and grammatical slips, e.g., 'Debby' vs 'Debbie', 'prof oundly', 'the n', 'wh en', 'in the base' should be 'in the basis', and 'stronger assumptions that those made in ConSol' should read 'than those'.","section":"Throughout"},{"comment":"Reference [17] is a YouTube video and is not an appropriate scholarly citation for a published paper; references [18] and [20] would benefit from full publication data.","section":"References"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a mixture of review and advocacy for the author's own interpretation (Convivial Solipsism). For a quantum foundations journal, the central no-go argument is not new, and the overclaim in the abstract and conclusion should be corrected. The paper could be suitable after revision if framed as a conditional no-go and a defense of ConSol, with the undoability caveat integrated into the main argument rather than relegated to a reservation. The self-citations are numerous but relevant; no misconduct is apparent."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"This paper is a decent entry-level review of the extended Wigner's Friend literature, but the title and abstract promise more than the argument delivers. The §4.3 derivation is faithfully taken from Schmid, Ying and Leifer, and I verified the Hardy-state probabilities myself: the equalities check out and the contradiction chain is valid given the five assumptions. The review part—original thought experiment, the various no-go theorems, the experimental approximations—is clear and would serve someone new to the topic. The author also deserves credit for flagging that photonic analogues are not conclusive.\n\nThe soft spot is the leap from a disjunctive no-go to the claim that events are not absolute. The five assumptions are jointly inconsistent, so the theorem tells you to drop at least one, not which one. The author's own §4.4 reservation directly targets assumption 5: if Wigner undoes Charlie's measurement, it is \"difficult to consider\" Charlie's result still a fact. When Alice or Bob chooses the undo setting, the relevant event is erased before the later outcomes are even defined, so the equalities that produce the contradiction presuppose the very absoluteness at issue. The paper gives no positive reason to prefer abandoning AOE over abandoning undoability; its own caveat points the other way. The abstract's \"no more possible to consider events as absolute\" is therefore stronger than the argument supports.\n\nConSol's no-disagreement property is asserted rather than derived, with the derivation deferred to a \"forthcoming work,\" so the positive proposal is not assessable here. As a review with an advocacy agenda, it is honest and competent; as a research paper establishing observer-relative events, it falls short.\n\nI would send this to peer review anyway, because the topic is important and the review portion is useful, but the referee should require a major reframing: the conclusion should be that the extended scenarios put pressure on absolute events while leaving open which assumption fails, and the ConSol consistency claim should be either derived or clearly labeled provisional. I would not cite it for the strong claim, but it could be a reasonable citation as a review. Bring it to reading group only if someone wants a one-stop survey of the area.","headline":"A competent review that overclaims: the no-go derivation is a disjunctive contradiction, and the paper's own undoability caveat undercuts the conclusion that events are observer-relative.","tokens_in":12791,"tokens_out":2084,"would_cite":false,"duration_ms":27745,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":["81P05","81P15"],"pacs":["03.65.Ta","03.65.Ud"],"model":"deepseek-v4-flash","headline":"The paper argues that quantum mechanics leaves no room for absolute measurement outcomes.","keywords":["Wigner's friend","extended Wigner's friend","absoluteness of observed events","measurement problem","no-go theorem","observer-relative facts","convivial solipsism","quantum foundations"],"falsifier":"A real experiment that attempts to undo the measurement record of a genuinely macroscopic observer and restore interference would settle the question: if the record cannot be re-cohered, the undoing assumption fails and events may be absolute; if it can, the no-go contradiction applies.","tokens_in":11623,"feed_emoji":"⚛️","tokens_out":12017,"duration_ms":126597,"temperature":0.7,"pith_summary":"This paper argues that the extended friend-in-the-box scenarios of quantum mechanics force a serious choice: either quantum mechanics is not universal, or measurement outcomes are not absolute facts shared by all observers. The argument is a no-go derivation in which five individually plausible assumptions lead to contradictory probability assignments in a single run. Since the first four assumptions---locality, no superdeterminism, universality of quantum mechanics, and absoluteness of observed events---look defensible, the paper follows the no-go literature in sacrificing the absoluteness of observed events. If that is right, an event is not a fixed point on a universal timeline but a fact established only relative to the observer who measures it, a picture that supports perspectival interpretations of quantum mechanics.","feed_headline":"No-go proof: measurement events are observer-relative, not absolute","feed_subtitle":"A nested-observer version of the friend-in-the-box experiment shows that absolute facts cannot survive universal quantum mechanics.","key_machinery":"The machine that carries the argument is the nested two-friend, two-observer setup. Two friends, each inside a sealed laboratory, share an entangled pair prepared in the Hardy state $\\psi = (|00\\rangle + |01\\rangle + |10\\rangle)/\\sqrt{3}$ and measure their particles in the 0/1 basis. Two external observers, Alice and Bob, can either ask a friend for the recorded result or undo that friend's measurement and measure in the $\\pm$ basis. The derivation uses four probability equalities, for instance $p(c{=}1,d{=}1 \\mid x{=}0,y{=}0)=0$ and $p(a{=}-,b{=}- \\mid x{=}1,y{=}1)=1/12$, and then locality projects them onto the single run with $x{=}1,y{=}1$. Those projected probabilities force the implication chain $(a=-) \\Rightarrow (d=1) \\Rightarrow (c=0) \\Rightarrow (b=+)$, making $p(a=-,b=-)=0$, which contradicts the value $1/12$ from the same run. That mechanical contradiction is what compels dropping one of the five assumptions, and the paper's stated resolution is to drop the absoluteness of observed events.","core_discovery":"The paper's central claim is that the extended two-friend, two-observer version of the friend-in-the-box scenario, run with a Hardy state, produces a contradiction for anyone who holds five assumptions at once: locality for observed events, no superdeterminism, universal validity of quantum mechanics, absoluteness of observed events, and the possibility of undoing a measurement. The derivation yields four probability equalities that, after a locality step, constrain a single run to satisfy both $p(a=-,b=-)=1/12$ and an implication chain forcing $p(a=-,b=-)=0$. Because the contradiction only arises if the same four results are taken to coexist, the paper concludes that at least one assumption must be dropped; in practice the one usually dropped is the absoluteness of observed events. That is the sense in which events are not absolute: an event has a definite occurrence or outcome only relative to the observer who measures it.","pith_inferences":["The paper leaves implicit that a fully relational account would need to say what 'probability' means when two observers' relative facts cannot be compared; this is a constraint any perspectival interpretation must satisfy.","The undoing premise suggests a concrete research direction: search for violations of interference at ever-larger record sizes, since a failure at some scale would replace the no-go contradiction with a boundary for quantum universality.","If the contradiction is right, standard quantum error correction and computation, which assume a single objective readout, may need a branch-relative notion of computation; this is not discussed in the paper.","The no-go result does not uniquely select the author's convivial solipsism; other perspectival readings could accommodate relative events, so the paper's interpretive conclusion goes beyond its formal result."],"forward_implications":["Under the five assumptions, no consistent assignment of absolute facts exists for the two-friend scenario; the same run must satisfy both $p(a=-,b=-)=0$ and $p(a=-,b=-)=1/12$, which is impossible if events are absolute.","The usual casualty is absoluteness of observed events: a result like 'Charlie got spin up' is true only relative to a designated observer, not as a fact of the universe.","There is no 'view from nowhere' in quantum mechanics; statements that combine two observers' results are not meaningful unless they are made from one observer's perspective.","Asking another observer for their result does not resolve the issue: the question-and-answer process is itself a measurement, and the answer heard is consistent with the asker's relative facts.","Photonic simulations of the friend are illustrative but not decisive, because an interaction with a photon is not clearly a measurement by an observer, and a real macroscopic undoing is beyond any conceivable technology."],"supporting_citations":[{"why":"Supplies the original friend-in-the-box scenario that the paper extends.","marker":"[1]"},{"why":"Defines the author's convivial solipsism interpretation, which the paper argues the relativity of events supports.","marker":"[2]"},{"why":"Introduces the first no-go theorem against observer-independent facts, the conclusion the paper defends.","marker":"[14]"},{"why":"Presents a later version of the same no-go theorem, reinforcing the claimed failure of absoluteness.","marker":"[15]"},{"why":"Provides the consistency argument showing quantum theory cannot describe its own use, a key member of the no-go family.","marker":"[16]"},{"why":"Gives a strong no-go theorem for the friend-in-the-box paradox that supports the paper's claim that absoluteness of observed events is usually abandoned.","marker":"[19]"},{"why":"Provides the simple derivation of the five-hypothesis contradiction that the paper reproduces.","marker":"[21]"},{"why":"Supplies the experimental approximation the paper evaluates and ultimately rules inconclusive.","marker":"[22]"}],"fun_headline_variants":["Quantum events may be observer-dependent, not absolute","Friend-in-box experiment shows events lack absoluteness","Observer-relative reality: no absolute quantum events","Wigner's friend extended: events are not absolute","Quantum facts are relative to the observer"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that an outside observer can in principle undo a friend's completed measurement, together with the locality-based step that transfers probabilities between different measurement settings; if either fails, the contradiction dissolves.","fun_headline_variants_meta":{"raw":{"variants":["Quantum events may be observer-dependent, not absolute","Friend-in-box experiment shows events lack absoluteness","Observer-relative reality: no absolute quantum events","Wigner's friend extended: events are not absolute","Quantum facts are relative to the observer"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000238,"raw_usage":{"total_tokens":1452,"prompt_tokens":831,"completion_tokens":621,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":447,"completion_tokens_details":{"reasoning_tokens":550}},"tokens_in":447,"tokens_out":621,"duration_ms":6948,"temperature":1.0,"reasoning_tokens":550,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T15:53:40.627165+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A real experiment that attempts to undo the measurement record of a genuinely macroscopic observer and restore interference would settle the question: if the record cannot be re-cohered, the undoing assumption fails and events may be absolute; if it can, the no-go contradiction applies.","supporting_citations":[{"cited_title":"Wigner, Remarks on the mind-body question, in I.J","cited_arxiv_id":null,"evidence_quote":"Supplies the original friend-in-the-box scenario that the paper extends."},{"cited_title":"Brukner, A no-go theorem for observer- independent facts, Entropy 20(5) (2018)","cited_arxiv_id":null,"evidence_quote":"Presents a later version of the same no-go theorem, reinforcing the claimed failure of absoluteness."},{"cited_title":"Frauchiger, R","cited_arxiv_id":null,"evidence_quote":"Provides the consistency argument showing quantum theory cannot describe its own use, a key member of the no-go family."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives a strong no-go theorem for the friend-in-the-box paradox that supports the paper's claim that absoluteness of observed events is usually abandoned."},{"cited_title":"Proietti, A","cited_arxiv_id":null,"evidence_quote":"Supplies the experimental approximation the paper evaluates and ultimately rules inconclusive."}],"review_version":1}