Abstract
Wigner-friend scenarios—in which an external agent describes quantum mechanically a laboratory in which a friend is making a measurement—give rise to possible inconsistencies due to the ambiguous character of quantum measurements. In this paper, we investigate Wigner-friend scenarios in which the external agents can probe in a noninvasive manner the dynamics inside the laboratories. We examine probes that can be very weakly coupled to the systems measured by the friends, or to the pointers or environments inside the laboratories. These couplings, known as weak measurements, are asymptotically small and do not change the outcomes obtained by the friends or their probabilities. Within our scheme, we show that the weakly coupled probes indicate to the external agents how to obtain consistent predictions, irrespective of the possible inconsistencies of quantum measurement theory. These noninvasive couplings could be implemented with present-day technologies.
- Received 28 August 2020
- Accepted 16 November 2020
DOI:https://doi.org/10.1103/PhysRevA.102.062204
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