Year: 2014
Type: article
Abstract: 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.
Source: Classical and Quantum Gravity
Authors: Dionigi M T Benincasa, Leron Borsten, Michel Buck, Fay Dowker
Institutions: Imperial College London, University of Waterloo
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, Government of Canada, Imperial College London, Institut Périmètre de physique théorique, Natural Sciences and Engineering Research Council of Canada, Engineering and Physical Sciences Research Council, Science and Technology Facilities Council, Kavli Institute for Theoretical Physics, University of California, Santa Barbara
OpenAlex ID: W2001654098