---
id: "20261028-0213-this-week-built-a"
title: "Does Aharonov's retrocausal two-state-vector formalism have documented contact with CS debates on retrocausality or computation?"
type: "capture"
status: "promoted"
origin: "batch"
promoted_to: ["30-notes/claim-lloyd-et-al-2010-p-ctc-paper-cites-aharonov-weak-value-and-aaronson-postselection.md","30-notes/claim-brun-wilde-2012-extends-p-ctc-aaronson-postselection-citation-chain-to-factoring.md","30-notes/claim-aaronson-2005-postselection-paper-cites-dorit-aharonov-not-yakir-aharonov.md","40-entities/entity-david-deutsch.md","40-entities/entity-charles-bennett.md","40-entities/entity-scott-aaronson.md","40-entities/entity-dorit-aharonov.md"]
not_promoted: ["Claim 4 (no documented contact found with the reversible-computation lineage — Landauer/Bennett/Toffoli): left in the inbox, not promoted to a claim-note. It is an absence-of-evidence finding after a genuinely non-exhaustive search, explicitly flagged in the capture itself as '[unverified — absence of a positive result, not a disconfirmed search]'. It is not load-bearing for any claim-note kept above, so per question-intake discipline it also does not warrant a new 50-questions entry; a future session that searches further may simply find the citation this one missed.","Further leads (2025 arXiv:2501.16335 experimental follow-up; Aaronson & Watrous 2009 D-CTC=PSPACE; Bennett/Leung/Smith/Smolin 2009 linearity-trap critique; Vaidman's own TSVF-and-computation research-topics page; Kastner 2002 and a 2022 retrocausal-weak-reality preprint) — left as unread leads, not promoted. None were read in full this session; none support a claim yet.","Seth Lloyd, and Todd Brun & Mark Wilde — entity candidates considered and not promoted to hub pages. Per the 2026-10-01 co-authorship ruling, co-authorship of one jointly-written paper is a mention, not a hub, absent a documented role beyond that paper; none of the three had independent standing established in this capture. Named inline in the three new claim-notes instead."]
writer_model: "claude-sonnet-5"
date_created: "2026-10-28T00:00:00.000Z"
provenance: "this batch run, 2026-10-28"
derived_from: []
tags: ["quantum-foundations","retrocausality","closed-timelike-curves","computational-complexity","aharonov","anti-echo-chamber","explore-2026-w44"]
seek_code_commit: "d40ee39"
---


Topic (explore thread, reflection 2026-W44): this week's Aharonov/Bohm/Bell
cluster and last week's Okon/Sudarsky/Wiedemann cluster are adjacent to each
other (via [[entity-sandu-popescu|Popescu]]) but neither touches the vault's
AI-history "home continent." This capture asks narrowly whether
[[entity-yakir-aharonov|Aharonov]]'s own retrocausal framework — the
[[entity-two-state-vector-formalism|two-state vector formalism]] and its
companion [[entity-weak-value|weak-value]] concept — has any documented
contact with computer-science debates on retrocausality, reversible
computation, or information-theoretic computation. Finding: yes, but the
contact is narrow, mediated, and one-directional — it runs through the
physics-of-closed-timelike-curves-as-computation literature, not through the
reversible-computation lineage (Landauer/Bennett/Toffoli) as such, and not
through any direct Aharonov–computer-scientist exchange.

## Claim: a 2010 physics paper on time-travel-as-computation cites Aharonov's weak-value paper directly, in the same breath as a quantum-complexity-theory result

Lloyd, Maccone, Garcia-Patron, Giovannetti, Shikano, Pirandola, Rozema,
Darabi, Soudagar, Shalm, and Steinberg's 2010 paper on postselected closed
timelike curves (P-CTCs) — a physically distinct alternative to David
Deutsch's quantum model of closed timelike curves, built instead on
quantum-teleportation-with-postselection — states that P-CTCs "share some
properties with the weak value interpretation of quantum mechanics,"
citing Aharonov, Albert, and Vaidman's 1988 Physical Review Letters paper
(the paper that introduced the weak value, the companion concept to the
two-state vector formalism) by name in its reference list (ref. [14]). In
the same paragraph, the paper separately invokes Scott Aaronson's 2005
result on the computational power of postselection (ref. [20]) to establish
that P-CTCs can efficiently solve problems in the complexity class PP. The
two citations — one to Aharonov's retrocausal/postselection program, one to
a computer-science complexity-theory result — sit side by side in the same
paper's argument for why time-travel-as-computation is powerful.

- source_url: https://arxiv.org/abs/1005.2219, source_sha: f8e881534aa540b1ac43d9512a3c67e66de3f606f3a523caa76023f44abd8282
- source_author: Seth Lloyd, Lorenzo Maccone, Raul Garcia-Patron, Vittorio Giovannetti, Yutaka Shikano, Stefano Pirandola, Lee A. Rozema, Ardavan Darabi, Yasaman Soudagar, Lynden K. Shalm, Aephraim M. Steinberg
- source_date: 2010-05-12 (arXiv v1; published as Phys. Rev. Lett. 106, 040403, 2011)
- source_title: "Closed timelike curves via post-selection: theory and experimental demonstration"
- source_venue: arXiv (author-submitted preprint; published in Physical Review Letters)
- source_quote: "Because they rely on post-selection, P-CTCs share some properties with the weak value interpretation of quantum mechanics [14], notably that there is no unique way to assign a definite state to the system in a CTC at a definite time."
- source_quote_2: "Aaronson's results on the power of postselection in quantum computing imply that the P-CTCs considered here permit the efficient solution of problems in PP [20]"
- source_tier: 1 (primary — author's own arXiv preprint, read in full via extract_pdf, both quotes quote_check-grounded)
- claim type: specific technical-mechanism claim (what the P-CTC paper's own argument cites and why) — clears the Tier 1-2 floor.

> [!note] Seek's commentary:
> This is the real find of the session: it answers the core question in the
> affirmative, but more narrowly than the topic's framing suggested. The
> contact isn't between Aharonov and computer science directly — it's
> between Aharonov's 1988 weak-value paper and a *third* paper's argument
> about time travel, which happens to also cite a computer scientist's
> result two lines later. Aharonov and Aaronson never cite each other;
> Lloyd et al. cite them both.

## Claim: the contact is sustained, not a one-off — a 2012 follow-up extends the same citation chain to concrete computational speedups

Brun and Wilde's 2012 *Foundations of Physics* paper builds directly on
Lloyd et al.'s P-CTC-computation result, explicitly deriving the same
PP-equivalence from Aaronson's postselection theorem, then uses it to
construct P-CTC-assisted circuits that efficiently factor integers and
solve problems in NP ∩ co-NP and in NP. The paper does not re-cite Aharonov
by name in the passages read, but it is a direct continuation of the same
citation chain established by Lloyd et al. — meaning the Aharonov-adjacent
weak-value framing recorded in the claim above is not an isolated citation
in one 2010 paper but part of an actively extended sub-literature (also
including a 2025 experimental follow-up, noted below under further leads)
on retrocausality-as-computation.

- source_url: https://arxiv.org/abs/1008.0433, source_sha: 32c1a7cd9d703d464410186893fb361e77635adbc96f8fbcf52c99636b156454
- source_author: Todd A. Brun, Mark M. Wilde
- source_date: submitted 2010 (arXiv v2, 2011-09-20); published in Foundations of Physics, 2012
- source_title: "Perfect state distinguishability and computational speedups with postselected closed timelike curves"
- source_venue: arXiv (author-submitted preprint; published in Foundations of Physics)
- source_quote: "Lloyd et al. have proven that the computational power of P-CTCs is equivalent to that of the complexity class PP [18, 19], by invoking Aaronson's results concerning the power of quantum computation with postselection [23]."
- source_tier: 1 (primary — author's own arXiv preprint, read in full via extract_pdf, quote quote_check-grounded)
- claim type: specific technical-mechanism claim — clears the floor.

## Claim: the contact is one-directional — Aaronson's own foundational postselection paper never engages Aharonov, weak values, or the two-state-vector formalism, and its one "Aharonov" citation is a different person entirely

Aaronson's 2005 paper defining PostBQP and proving PostBQP = PP — the exact
result both P-CTC papers above lean on — was read in full. It cites "D.
Aharonov" twice in its reference list (a survey on Quantum NP with T. Naveh,
and a paper on lattice problems with O. Regev), but this is Dorit Aharonov,
a computer scientist and complexity theorist (and, incidentally, Yakir
Aharonov's daughter) — not Yakir Aharonov, and not a citation to weak
values, retrocausality, or the two-state vector formalism in any form. The
paper contains no reference to postselection's retrocausal interpretation at
all; "postselection" here is treated purely as a computational primitive
(discarding runs where an event fails to occur), with no engagement with
the foundational debate over what postselection means physically. The
documented contact between Aharonov's retrocausal program and CS complexity
theory therefore runs in exactly one direction: physicists writing about
time-travel-as-computation reached for Aharonov's weak-value paper to
describe their own result; the complexity theorist whose result they
reached for never engaged Aharonov's program, and shares a surname with a
different Aharonov by coincidence.

- source_url: https://arxiv.org/abs/quant-ph/0412187, source_sha: 7e05821eaae96aaf8f1b9a1bf2575ae02258b3f364ce0822e628445607a7243e
- source_author: Scott Aaronson
- source_date: 2004-12-23 (arXiv v1; published Proc. R. Soc. A 461, 3473, 2005)
- source_title: "Quantum Computing, Postselection, and Probabilistic Polynomial-Time"
- source_venue: arXiv (author-submitted preprint; published in Proceedings of the Royal Society A)
- source_quote: "D. Aharonov and T. Naveh. Quantum NP - a survey. quant-ph/0210077, 2002." / "D. Aharonov and O. Regev. Lattice problems in NP intersect coNP."
- source_tier: 1 (primary — author's own arXiv preprint, read in full via extract_pdf)
- claim type: historical/bibliographic claim (who is and isn't cited) — Tier 3-4 floor would suffice, but this rests on a direct primary read, so it clears Tier 1-2 as well.

> [!note] Seek's commentary:
> Worth stating plainly for anyone who searches this vault later for
> "Aharonov + Aaronson": there is no such pairing. The near-miss (same
> surname, actually related people, zero shared citation) is exactly the
> kind of false-positive a keyword search would manufacture, and it's worth
> having on record that a direct read ruled it out rather than leaving the
> coincidence to be rediscovered and half-trusted later.

## Claim: no documented contact was found with the reversible-computation lineage specifically (Landauer/Bennett/Toffoli), distinguishing it from the retrocausality-as-computation contact above

Searches for Aharonov, the two-state vector formalism, or weak values
alongside Landauer, Bennett, or Toffoli's reversible-computation lineage —
and a direct read of Frank and Shukla's 2021 "Quantum Foundations of
Classical Reversible Computing" survey's reference list — surfaced no
citation linking the two literatures. Reversible computation's own
foundational papers (Landauer 1961, Bennett 1973) and its quantum-era
descendants cite each other and the physics of computation generally, but
not Aharonov's retrocausal program specifically, in anything found this
session. This narrows the answer to the topic's three-part question
(retrocausality / reversible computation / information-theoretic
computation): documented contact exists for retrocausality-as-computation
(the CTC literature above), not for reversible computation as its own
lineage. This is a negative finding after a genuine but not exhaustive
search — later sessions may find a citation this one missed.

- claim type: historical claim resting on absence of evidence — marked
  explicitly as a search result, not a proof of non-existence.
- `[unverified — absence of a positive result, not a disconfirmed search]`

## Further leads

- A 2025 experimental paper (arXiv:2501.16335) extends P-CTC theory to
  simulate recovering scrambled quantum information — not read in full;
  worth checking whether it re-engages Aharonov's weak-value framing
  directly or only inherits it via the Lloyd et al./Brun & Wilde chain.
- Aaronson and Watrous's 2009 *Proc. Roy. Soc. A* paper proving Deutsch's
  (D-CTC) model has computational power equal to PSPACE is the parallel,
  competing branch to the P-CTC line above — not read in full this session;
  would clarify whether Deutsch's own model (as opposed to the
  Aharonov-adjacent P-CTC model) has any independent Aharonov connection.
- Bennett, Leung, Smith, and Smolin's 2009 PRL critique of D-CTC
  computational claims (the "linearity trap" argument referenced inside the
  Brun & Wilde paper) — not read; Charles Bennett appears in this cluster in
  two separate roles (reversible-computation founder, 1973; and originator
  of the postselected-teleportation CTC suggestion that Lloyd et al. built
  on) and that double role was not independently verified beyond the two
  papers read here.
- Lev Vaidman's own "Quantum Communication, Cryptography and Computation"
  research-topics listing (tau.ac.il) surfaced in search but was not opened
  directly — worth checking whether Vaidman himself, rather than a later
  citing paper, ever wrote directly on TSVF and computation.
- R.E. Kastner's 2002 arXiv paper arguing retrocausality implies restricted
  weak values, and a 2022 arXiv "retrocausal weak reality" paper citing
  Aharonov–Vaidman — both surfaced in search as philosophy-of-physics
  retrocausality literature, not computer-science; not read in full, listed
  here as adjacent but off-topic for this capture's CS-contact question.

## Entity candidates

- David Deutsch — person — originated the 1991 quantum model of closed
  timelike curves (D-CTCs) that every paper in this cluster explicitly
  measures itself against ("physically inequivalent to Deutsch's"); the
  older foundational figure the whole P-CTC-computation line is a
  contrast-case against, not a co-author of it.
- Charles H. Bennett — person — IBM researcher credited in two separate
  roles inside this cluster: as the 1973 founder of reversible-computation
  theory ("Logical Reversibility of Computation"), and, decades later, as
  the originator (with Benjamin Schumacher) of the postselected-teleportation
  suggestion that the entire P-CTC branch is built on — the literal bridge
  node between reversible computation and the Aharonov-descended
  postselection framework, though the two roles were not found directly
  linked to each other in any source read this session.
- Scott Aaronson — person — defined PostBQP and proved PostBQP = PP (2005);
  his result is the computer-science half of the citation pairing found in
  claim 1, cited by Lloyd et al. two lines after Aharonov's weak-value paper.
- Seth Lloyd — person — lead author of the 2010 paper that performs the
  actual citation bridging Aharonov's weak-value paper to Aaronson's
  complexity result; MIT quantum-information theorist.
- Todd A. Brun and Mark M. Wilde — person (pair) — authors of the 2012
  follow-up extending the P-CTC computational-speedup result to factoring
  and NP ∩ co-NP.
- Dorit Aharonov — person — Yakir Aharonov's daughter and an independent
  quantum-complexity theorist in her own right (QCMA, lattice problems);
  cited in Aaronson's 2005 paper under the same surname as Yakir, with zero
  connection to his retrocausal program — flagged specifically to prevent a
  future keyword search from conflating the two.