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We study the paradoxical aspects of closed time-like curves and their impact on the theory of computation. After introducing the $\text{TM}_\text{CTC}$, a classical Turing machine benefiting CTCs for backward time travel, Aaronson et al.…

Computational Complexity · Computer Science 2023-01-30 Sara Babaee Khanehsar , Farzad Didehvar

The fact that closed timelike curves (CTCs) are permitted by general relativity raises the question as to how quantum systems behave when time travel to the past occurs. Research into answering this question by utilising the quantum circuit…

Quantum Physics · Physics 2014-10-13 John-Mark A. Allen

Recently Burrage, de Rham, Heisenberg and Tolley have constructed eternal, classical solutions with closed timelike curves (CTCs) in a Galileon model coupled to an auxiliary scalar field. These theories contain at least two distinct metrics…

High Energy Physics - Theory · Physics 2012-11-20 Jarah Evslin

Toy models for quantum evolution in the presence of closed timelike curves (CTCs) have gained attention in the recent literature due to the strange effects they predict. The circuits that give rise to these effects appear quite abstract and…

Quantum Physics · Physics 2013-05-30 J. L. Pienaar , C. R. Myers , T. C. Ralph

General relativity predicts the existence of closed timelike curves (CTCs), along which an object could travel to its own past. A consequence of CTCs is the failure of determinism, even for classical systems: one initial condition can…

Quantum Physics · Physics 2021-05-20 Lachlan G. Bishop , Fabio Costa , Timothy C. Ralph

Any given prescription of quantum time travel necessarily endows a Hilbert space to the chronology-violating (CV) system on the closed timelike curve (CTC). However, under the two foremost models, Deutsch's prescription (D-CTCs) and…

Quantum Physics · Physics 2025-02-10 Lachlan G. Bishop , Fabio Costa , Timothy C. Ralph

We study the power of closed timelike curves (CTCs) and other nonlinear extensions of quantum mechanics for distinguishing nonorthogonal states and speeding up hard computations. If a CTC-assisted computer is presented with a labeled…

Quantum Physics · Physics 2009-10-29 Charles H. Bennett , Debbie Leung , Graeme Smith , John A. Smolin

The possible existence of closed timelike curves (CTCs) draws attention to fundamental questions about what is physically possible and what is not. An example is the "no cloning theorem" in quantum mechanics, which states that no physical…

Quantum Physics · Physics 2015-06-05 D. Ahn , C. R. Myers , T. C. Ralph , R. B. Mann

Generalized quantum mechanics is used to examine a simple two-particle scattering experiment in which there is a bounded region of closed timelike curves (CTCs) in the experiment's future. The transitional probability is shown to depend on…

High Energy Physics - Theory · Physics 2009-10-30 Seth Rosenberg

The conceptual definition and understanding of time, both quantitatively and qualitatively is of the utmost difficulty and importance. As time is incorporated into the proper structure of the fabric of spacetime, it is interesting to note…

General Relativity and Quantum Cosmology · Physics 2013-10-21 Francisco S. N. Lobo

In the study of quantum computation, data is represented in terms of linear operators which form a generalized model of probability, and computations are most commonly described as products of unitary transformations, which are the…

Quantum Physics · Physics 2008-12-16 Jonathan Robert Niel de Beaudrap

In a recent Letter, Bennett and coworkers [1] argue that proofs of exotic quantum effects using closed timelike curves (CTC's) based on the work of Deutsch [2], or other nonlinear quantum dynamics, suffer from a fallacy that they call the…

Quantum Physics · Physics 2010-06-10 Eric G. Cavalcanti , Nicolas C. Menicucci

The spacetime metric around a rotating SuperConductive Ring (SCR) is deduced from the gravitomagnetic London moment in rotating superconductors. It is shown that theoretically it is possible to generate Closed Timelike Curves (CTC) with…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Clovis Jacinto de Matos

Closed timelike curves are among the most controversial features of modern physics. As legitimate solutions to Einstein's field equations, they allow for time travel, which instinctively seems paradoxical. However, in the quantum regime…

Quantum Physics · Physics 2015-01-22 Martin Ringbauer , Matthew A. Broome , Casey R. Myers , Andrew G. White , Timothy C. Ralph

In this comment on S.Lloyd, et al, Phys.Rev.Lett. 106, 040403 (2011), we show that modelling closed timelike curves (CTCs) as post-selected teleportation allows signalling to past times before the creation of the CTC and allows information…

Quantum Physics · Physics 2011-07-26 T. C. Ralph

We use techniques of quantum information theory to analyze the quantum causal histories approach to quantum gravity. We show that while it is consistent to introduce closed timelike curves (CTCs), they cannot generically carry independent…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Etera R. Livine , Daniel R. Terno

We give a detailed account of the one-way quantum computer, a scheme of quantum computation that consists entirely of one-qubit measurements on a particular class of entangled states, the cluster states. We prove its universality, describe…

Quantum Physics · Physics 2009-11-10 R. Raussendorf , D. E. Browne , H. J. Briegel

The one-way quantum computer (QCc) is a universal scheme of quantum computation consisting only of one-qubit measurements on a particular entangled multi-qubit state, the cluster state. The computational model underlying the QCc is…

Quantum Physics · Physics 2007-05-23 R. Raussendorf , H. J. Briegel

We define a new quantity we call a ctcbit that provides a means for quantifying a qubit on a closed time-like curve (CTC) as a shared resource. We describe a simple protocol for the sharing of information that is similar to quantum…

Quantum Physics · Physics 2008-12-25 Ian T. Durham

Notoriously, the Einstein equations of general relativity have solutions in which closed timelike curves (CTCs) occur. On these curves time loops back onto itself, which has exotic consequences. However, in order to make time travel stories…

General Relativity and Quantum Cosmology · Physics 2021-05-26 Ruward A. Mulder , Dennis Dieks