---
title: "Lloyd et al.'s 2010 postselected-closed-timelike-curve paper cites Aharonov's weak-value paper and Aaronson's postselection result in the same argument"
type: "claim"
status: "seedling"
source_url: "https://arxiv.org/abs/1005.2219"
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: "2010-05-12T00:00:00.000Z"
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 post-selection in quantum computing imply that the P-CTCs considered here permit the efficient solution of problems in PP [20]"
source_tier: 1
source_sha: "f8e881534aa540b1ac43d9512a3c67e66de3f606f3a523caa76023f44abd8282"
source_venue: "arXiv (author-submitted preprint; published as Phys. Rev. Lett. 106, 040403, 2011)"
audit_status: "capture-verified | 2026-10-30 cross-model audit (claude-fable-5): PDF re-fetched live, byte-identical to the capture (sha f8e88153…); both quotes re-confirmed against the paper, and refs [14] (Aharonov/Albert/Vaidman PRL 60, 1351, 1988) and [20] (Aaronson, Proc. Roy. Soc. A 461, 3473, 2005) match the note's attributions. CORRECTED two defects: (1) the body claimed the two citations sit 'in the same paragraph... two lines apart' — in the paper the weak-value sentence is in the P-CTC-mechanism paragraph (p.2) and the Aaronson sentence in the computational-power paragraph (p.3), about a page apart; body and commentary re-worded. (2) source_quote_2 had de-hyphenated a line-break as 'postselection'; the paper prints 'post-selection' consistently (abstract and body), quote corrected."
provenance: "Promotion from 10-inbox/raw/2026-10-28-this-week-built-a-second-independent-quantum-foundations.md, 2026-10-28"
origin: "batch"
derived_from: ["10-inbox/raw/2026-10-28-this-week-built-a-second-independent-quantum-foundations.md"]
date_created: "2026-10-28T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["quantum-foundations","retrocausality","closed-timelike-curves","postselection","aharonov","aaronson","computational-complexity"]
seek_code_commit: "d40ee39"
quote_sweep: "PASS 2026-10-29 — source_quote verbatim (normalized) in the capture-time archive (sha256 f8e881534aa5…) [reading-order], same-night model-free sweep"
verified_verbatim: "2026-10-29 — source_quote matched verbatim (normalized) against a direct fetch of source_url by seek_verify (no model involved)"
---


Lloyd, Maccone, Garcia-Patron, Giovannetti, Shikano, Pirandola, Rozema, Darabi, Soudagar, Shalm, and Steinberg's 2010 paper "Closed timelike curves via post-selection: theory and experimental demonstration" proposes postselected closed timelike curves (P-CTCs), built on quantum-teleportation-with-postselection, as a physically distinct alternative to [[entity-david-deutsch|David Deutsch]]'s 1991 quantum model of closed timelike curves (D-CTCs). In motivating the P-CTC construction, the paper states that P-CTCs "share some properties with the [[entity-weak-value|weak value]] interpretation of quantum mechanics," citing Aharonov, Albert, and [[entity-lev-vaidman|Vaidman]]'s 1988 paper that introduced the weak value (the companion concept to [[entity-yakir-aharonov|Yakir Aharonov]]'s [[entity-two-state-vector-formalism|two-state vector formalism]]; see [[claim-aharonov-1988-weak-value-origin-disturbance-scales-epsilon-squared]]). In a separate, later paragraph — on the computational power of CTCs, about a page further on — the paper invokes [[entity-scott-aaronson|Scott Aaronson]]'s 2005 result on the computational power of postselection to establish that P-CTCs can efficiently solve problems in the complexity class PP.

This is the documented point of contact between Aharonov's retrocausal/postselection program and computer-science complexity theory: not a direct citation between Aharonov and a computer scientist, but a third paper's argument that cites both — in two different paragraphs about a page apart, each hanging off the same premise, that P-CTCs rest on post-selection — to motivate why postselection-based time travel is computationally powerful. The citation chain continues in [[claim-brun-wilde-2012-extends-p-ctc-aaronson-postselection-citation-chain-to-factoring]].

> [!note] Seek's commentary:
> The satisfying part of this find is how narrow it turned out to be once traced. "Does Aharonov's program touch computer science" sounds like it should resolve to a handshake between two people; instead it resolves to two passages of a single four-page paper, written by physicists building a time-machine thought experiment, who happened to need both citations to make their point land. Contact, but mediated, incidental to both of the people it connects, and load-bearing only for the paper doing the connecting.
> — Seek