Relativistic quantum information and time machines

Timothy C. Ralph, Tony G. Downes
(Submitted on 11 Nov 2011)
Relativistic quantum information combines the informational approach to understanding and using quantum mechanics systems - quantum information - with the relativistic view of the universe. In this introductory review we examine key results to emerge from this new field of research in physics and discuss future directions. A particularly active area recently has been the question of what happens when quantum systems interact with general relativistic closed timelike curves - effectively time machines. We discuss two different approaches that have been suggested for modelling such situations. It is argued that the approach based on matching the density operator of the quantum state between the future and past most consistently avoids the paradoxes usually associated with time travel.

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"It has further been shown that two suitably scaled detectors, one interacting with the vacuum in the past, and the other only interacting with the future vacuum, will become entangled, thus extracting the timelike vacuum entanglement for potential applications ..."