Classical field approach to quantum weak measurements.
By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between pre- and postselection boundary conditions. The classical field is itself a weak value of the corresponding quantum field operator and satisfies equations of motion that extremize an effective action. Weak measurements perturb this effective action, producing measurable changes to the classical field dynamics. As such, weakly measured effects always correspond to an effective classical field. This general result explains why these effects appear to be robust for pre- and postselected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field.
Center for Emergent Matter Science, RIKEN, Saitama 351-0198, Japan.
Justin
J
Dressel
Interdisciplinary Theoretical Science Research Group, RIKEN, Saitama 351-0198, Japan.
Konstantin Y
KY
Bliokh
Center for Emergent Matter Science, RIKEN, Saitama 351-0198, Japan and Physics Department, University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
Franco
F
Nori