Gentle Measurement as a Principle of Quantum Theory

TL;DR

This paper introduces the gentle measurement principle (GMP) as a foundational concept in quantum mechanics, demonstrating its implications for measurement uncertainty, nonlocality limits, and information-theoretic constraints that distinguish quantum theory from other probabilistic theories.

Contribution

It establishes GMP as a fundamental principle that constrains physical laws and differentiates quantum theory from other probabilistic frameworks within a general probabilistic theories setting.

Findings

GMP limits measurement uncertainty and nonlocality.

GMP enforces the chain inequality for conditional entropy.

GMP helps distinguish quantum theory from stretched probabilistic theories.

Abstract

We propose the gentle measurement principle (GMP) as one of the principles at the foundation of quantum mechanics. It asserts that if a set of states can be distinguished with high probability, they can be distinguished by a measurement that leaves the states almost invariant, including correlation with a reference system. While GMP is satisfied in both classical and quantum theories, we show, within the framework of general probabilistic theories, that it imposes strong restrictions on the law of physics. First, the measurement uncertainty of a pair of observables cannot be significantly larger than the preparation uncertainty. Consequently, the strength of the CHSH nonlocality cannot be maximal. The parameter in the stretched quantum theory, a family of general probabilistic theories that includes the quantum theory, is also limited. Second, the conditional entropy defined in terms of a data compression theorem satisfies the chain inequality. Not only does it imply information causality and Tsirelson's bound, but it singles out the quantum theory from the stretched one. All these results show that GMP would be one of the principles at the heart of quantum mechanics.