Wigner Friend scenarios with non-invasive weak measurements

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.

Slightly extended Discussion Section, as well as minor changes for improved readability. Similar to published version. To be published in PRA

References in corpus (4)

• Proofs of nonlocality without inequalities revisited
• Bohmian mechanics, the quantum-classical correspondence and the classical limit: the case of the square billiard
• Decoherence framework for Wigner's friend experiments
• Wigner's friend, Feynman's paths and material records

Cited by in corpus (7)

• The original Wigner's friend paradox within a realist toy model
• Quantum measurements with, and yet without an Observer
• Extended Wigner's friend problem and the internal consistency of standard quantum mechanics
• Classical information and collapse in Wigner's friend setups
• From observer-dependent facts to frame-dependent measurement records in Wigner friend scenarios
• Demonstration of quantum correlations that are incompatible with absoluteness of measurement
• Making sense of relativistic Wigner friend scenarios: a problem for unitary accounts of quantum measurements ?