# Experimental self-characterization of quantum measurements

## TL;DR

This paper introduces a self-characterization method for quantum measurements that reconstructs the response range without relying on known probe states, achieving high fidelity results and enabling device-independent quantum protocols.

## Contribution

The authors develop a novel range-based self-characterization technique for quantum measurements that bypasses the need for accurately known probe states.

## Key findings

- Achieved fidelities above 99.99% with conventional tomography.
- Successfully characterized photonic quantum measurements using the new method.
- Paves the way for device-independent quantum information protocols.

## Abstract

The accurate and reliable description of measurement devices is a central problem in both observing uniquely non-classical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum tomography is the prevalent tool to characterize quantum detectors. However, such a characterization relies on accurately characterized probe states, rendering reliability of the characterization lost in circular argument. Here we report a self-characterization method of quantum measurements based on reconstructing the response range, the entirety of attainable measurement outcomes, eliminating the reliance on known states. We characterize two representative measurements implemented with photonic setups and obtain fidelities above 99.99% with the conventional tomographic reconstructions. This initiates range-based techniques in characterizing quantum systems and foreshadows novel device-independent protocols of quantum information applications.