Spin operator, Bell nonlocality and Tsirelson bound in quantum-gravity induced minimal-length quantum mechanics

TL;DR

This paper explores how a minimal length scale in quantum gravity modifies the spin operator, leading to enhanced quantum nonlocality and violations of the Bell inequality beyond Tsirelson's bound, with potential experimental tests.

Contribution

It demonstrates that minimal-length quantum mechanics alters the spin operator and can produce stronger Bell nonlocality than standard quantum mechanics.

Findings

Spin operator gains momentum dependence due to minimal length.

Violations of Bell inequality can surpass Tsirelson bound.

Proposed experimental setups for testing these effects.

Abstract

Different approaches to quantum gravity converge in predicting the existence of a minimal scale of length. This raises the fundamental question as to whether and how an intrinsic limit to spatial resolution can affect quantum mechanical observables associated to internal degrees of freedom. We answer this question in general terms by showing that the spin operator acquires a momentum-dependent contribution in quantum mechanics equipped with a minimal length. Among other consequences, this modification induces a form of quantum nonlocality stronger than the one arising in ordinary quantum mechanics. In particular, we show that violations of the Bell inequality can exceed the maximum value allowed in ordinary quantum mechanics, the so-called Tsirelson bound, by a positive-valued function of the momentum operator. We introduce possible experimental settings based on neutron interferometry and quantum contextuality, and we provide preliminary estimates on the values of the physical parameters needed for actual laboratory implementations.