State-dependent rotations of spins by weak measurements

TL;DR

This paper demonstrates that weak measurements induce state-dependent rotations in quantum systems, providing constraints that challenge certain hidden-variable theories and deepen understanding of quantum measurement effects.

Contribution

It introduces a new perspective on how weak measurements affect quantum states and constrains hidden-variable theories more directly than before.

Findings

Weak measurements produce state-dependent rotations.

Constraints on hidden-variable theories are strengthened.

Crypto-nonlocal hidden-variable theories are ruled out.

Abstract

IIt is shown that a weak measurement of a quantum system produces a new state of the quantum system which depends on the prior state, as well as the (uncontrollable) measured position of the pointer variable of the weak measurement apparatus. The result imposes a constraint on hidden-variable theories which assign a different state to a quantum system than standard quantum mechanics. The constraint means that a crypto-nonlocal hidden-variable theory can be ruled out in a more direct way than previously.