Nonlocal appearance of a macroscopic angular momentum

TL;DR

The paper explores a thought experiment where measuring a few atoms creates a large angular momentum nonlocally, highlighting quantum nonlocality without violating conservation laws.

Contribution

It introduces a measurement scheme demonstrating nonlocal creation of macroscopic angular momentum without violating conservation of angular momentum.

Findings

Measurement can induce nonlocal macroscopic angular momentum

No violation of angular momentum conservation occurs

Highlights counter-intuitive quantum features

Abstract

We discuss a type of measurement in which a macroscopically large angular momentum (spin) is "created" nonlocally by the measurement of just a few atoms from a double Fock state. This procedure apparently leads to a blatant nonconservation of a macroscopic variable - the local angular momentum. We argue that while this gedankenexperiment provides a striking illustration of several counter-intuitive features of quantum mechanics, it does not imply a non-local violation of the conservation of angular momentum.