# Unified framework for quantumness -- coherence, discord, and entanglement

## TL;DR

This paper proposes a unified operational framework for quantumness that encompasses coherence, discord, and entanglement, clarifying their interrelations and transformations within interferometry-based scenarios.

## Contribution

It introduces a general, operationally motivated framework that unifies different measures of quantumness and elucidates their fundamental connections and transformations.

## Key findings

- Unified framework based on interferometry
- Clarifies relationships among coherence, discord, and entanglement
- Framework extends to other quantum scenarios

## Abstract

From an operational perspective, quantumness characterizes the exotic behavior in a physical process which cannot be explained with Newtonian physics. There are several widely used measures of quantumness, including coherence, discord, and entanglement, each proven to be essential resources in particular situations. There exists evidence of fundamental connections amongst the three measures. However, those quantumnesses are still regarded differently and such connections are yet to be elucidated. Here, we introduce a general framework of defining a unified quantumness with an operational motivation founded on the capability of interferometry. The quantumness appears differently as coherence, discord, and entanglement in different scenarios with local measurement, weak reference frame free measurement, and strong reference frame free measurement, respectively. Our results also elaborate how these three measures are related and how they can be transformed from each other. This framework can be further extended to other scenarios and serves as a universal quantumness measure.