Partial measurements and the realization of quantum-mechanical counterfactuals

TL;DR

This paper introduces partial measurements as a tool to understand quantum counterfactuals, revealing how their reversible nature impacts foundational principles and non-local quantum phenomena.

Contribution

It demonstrates how partial measurements can be used to reinterpret quantum paradoxes and non-locality, challenging the idea of wavefunction realism.

Findings

Partial measurements can be probabilistically reversed.

Reformulating quantum paradoxes with partial measurements yields counter-intuitive results.

Results suggest abandoning wavefunction realism to resolve paradoxes.

Abstract

We propose partial measurements as a conceptual tool to understand how to operate with counterfactual claims in quantum physics. Indeed, unlike standard von Neumann measurements, partial measurements can be reversed probabilistically. We first analyze the consequences of this rather unusual feature for the principle of superposition, for the complementarity principle, and for the issue of hidden variables. Then we move on to exploring non-local contexts, by reformulating the EPR paradox, the quantum teleportation experiment, and the entanglement-swapping protocol for the situation in which one uses partial measurements followed by their stochastic reversal. This leads to a number of counter-intuitive results, which are shown to be resolved if we give up the the idea of attributing reality to the wavefunction of a single quantum system.