Wigner Friend scenarios with non-invasive weak measurements

TL;DR

This paper explores Wigner Friend scenarios using non-invasive weak measurements to resolve potential inconsistencies in quantum measurement descriptions, demonstrating that weak probes can guide consistent predictions without disturbing the system.

Contribution

It introduces a method employing weak measurements within Wigner Friend scenarios to achieve consistent quantum predictions despite measurement ambiguities.

Findings

Weak measurements do not alter measurement outcomes.

Probes can guide external agents to consistent predictions.

Implementation feasible with current technology.

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 work, we investigate Wigner Friend scenarios in which the external agents can probe in a non-invasive 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 nor 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 non-invasive couplings could be implemented with present-day technologies.