Do qubits dream of entangled sheep? Quantum measurement without classical output

TL;DR

This paper introduces a novel quantum measurement concept called 'sensation' that models quantum agents experiencing the world through quantum sensors, challenging classical assumptions and offering new insights into quantum information flow.

Contribution

The work proposes an entirely quantum notion of measurement, called sensation, which describes quantum agents with coherent quantum memories and reframes measurement without classical outputs.

Findings

Sensations always disturb at least as much as they inform.

Quantification of information gain and disturbance using quantum information theory.

Potential implications for understanding quantum networks and the quantum-classical boundary.

Abstract

Quantum mechanics is usually formulated with an implicit assumption that agents who can observe and interact with the world are external to it and have a classical memory. However, there is no accepted way to define the quantum-classical cut and no a priori reason to rule out fully quantum agents with coherent quantum memories. In this work, we introduce an entirely quantum notion of measurement, called a sensation, to account for quantum agents that experience the world through quantum sensors. Sensations eschew probabilities and instead describe a deterministic flow of quantum information. We quantify the information gain and disturbance of a sensation using concepts from quantum information theory and find that sensations always disturb at least as much as they inform. Viewing measurements as sensations could lead to a new understanding of quantum theory in general and to new results in the context of quantum networks.