On sequential measurements with indefinite causal order

Two projective measurements sequentially performed on a quantum system is studied in the case that the order of the measurements is completely indefinite. The interference of the different orders provides the Kirkwood-Dirac distribution of a quantum system to be measured and thus the weak value of an observable can be obtained without weak measurement. In an interferometric setting, the Kirkwood-Dirac distribution can be constructed from conditional visibility and phase shift. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study examines two projective measurements performed sequentially on a quantum system with completely indefinite order. The interference of different orders allows for the determination of the Kirkwood-Dirac distribution of the quantum system being measured, enabling the extraction of a weak value of an observable without the need for weak measurement. In an interferometric setting, the Kirkwood-Dirac distribution can be constructed from conditional visibility and phase shift.