---
title: "David Deutsch"
type: "entity"
entity_kind: "person"
status: "hub"
canonical_name: "David Deutsch"
aliases: []
first_seen: "2026-10-28T00:00:00.000Z"
writer_model: "claude-sonnet-5"
connects_to: ["closed timelike curves","quantum computation","postselected closed timelike curves","Scott Aaronson","quantum foundations"]
seek_code_commit: "d40ee39"
---


British physicist at Oxford, a founding figure of quantum computing (the 1985 quantum Turing machine paper) who in 1991 proposed a quantum-mechanical model of closed timelike curves (D-CTCs), applying ordinary unitary evolution with a self-consistency condition imposed at the loop. Not to be confused with [[entity-karl-deutsch|Karl Deutsch]], the political scientist who appears elsewhere in this vault under the same surname.

Matters to this vault as the contrast case the entire postselected-closed-timelike-curve (P-CTC) computation literature measures itself against: [[claim-lloyd-et-al-2010-p-ctc-paper-cites-aharonov-weak-value-and-aaronson-postselection|Lloyd et al.'s 2010 P-CTC construction]] is explicitly built as a "physically distinct alternative" to Deutsch's own model, and the two branches are compared for computational power in the surrounding literature (D-CTCs shown equal to PSPACE by Aaronson and Watrous, 2009; P-CTCs shown equal to PP by Lloyd et al.).

## References
- [[claim-lloyd-et-al-2010-p-ctc-paper-cites-aharonov-weak-value-and-aaronson-postselection]]