Back-from-the-future at MIT - Seth Lloyd on Yakir Aharonov's QM

Phys. Rev. Lett. 106, 040403 (2011) [4 pages]
Closed Timelike Curves via Postselection: Theory and Experimental Test of Consistency
Abstract
Seth Lloyd1, Lorenzo Maccone1, Raul Garcia-Patron1, Vittorio Giovannetti2, Yutaka Shikano1,3, Stefano Pirandola1, Lee A. Rozema4, Ardavan Darabi4, Yasaman Soudagar4, Lynden K. Shalm4, and Aephraim M. Steinberg4
1xQIT, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
2NEST-CNR-INFM & Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa, Italy
3Department of Physics, Tokyo Institute of Technology, 2-12-1 Oh-Okayama, Meguro, Tokyo, 152-8551, Japan
4CQIQC, IOS, Department of Physics, University of Toronto, Canada M5S 1A7
Received 12 May 2010; revised 22 November 2010; published 27 January 2011

"Closed timelike curves (CTCs) are trajectories in spacetime that effectively travel backwards in time: a test particle following a CTC can interact with its former self in the past. A widely accepted quantum theory of CTCs was proposed by Deutsch. Here we analyze an alternative quantum formulation of CTCs based on teleportation and postselection, and show that it is inequivalent to Deutsch’s. The predictions or retrodictions of our theory can be simulated experimentally: we report the results of an experiment illustrating how in our particular theory the “grandfather paradox” is resolved. ...

A user that has access to a closed timelike curve might be able to distinguish nonorthogonal states [20] and per- form computations very efficiently"