Quantum information processing and relativistic quantum fields

Dionigi M.T. Benincasa, Leron Borsten, Michel Buck, Fay Dowker

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)


It is shown that an ideal measurement of a one-particle wave packet state of a relativistic quantum field in Minkowski spacetime enables superluminal signalling. The result holds for a measurement that takes place over an intervention region in spacetime whose extent in time in some frame is longer than the light-crossing time of the packet in that frame. Moreover, these results are shown to apply not only to ideal measurements but also to unitary transformations that rotate two orthogonal one-particle states into each other. In light of these observations, possible restrictions on the allowed types of intervention are considered. A more physical approach to such questions is to construct explicit models of the interventions as interactions between the field and other quantum systems such as detectors. The prototypical Unruh-DeWitt detector couples to the field operator itself and so most likely respects relativistic causality. On the other hand, detector models which couple to a finite set of frequencies of field modes are shown to lead to superluminal signalling. Such detectors do, however, provide successful phenomenological models of atom-qubits interacting with quantum fields in a cavity but are valid only on time scales many orders of magnitude larger than the light-crossing time of the cavity.

Original languageEnglish
Article number075007
JournalClassical and Quantum Gravity
Issue number7
Publication statusPublished - 7 Apr 2014


  • measurement
  • quantum fields
  • relativistic quantum information


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