Entanglement-based single-shot detection of a single magnon with a superconducting qubit

TL;DR

This paper demonstrates a novel method for detecting single magnons using a superconducting qubit, leveraging entanglement and single-shot measurement, advancing quantum sensing capabilities in magnonics.

Contribution

It introduces a new entanglement-based single-shot detection technique for single magnons with high quantum efficiency, bridging quantum magnonics and superconducting qubit technology.

Findings

Achieved single magnon detection with 0.71 quantum efficiency.

Established entanglement-based single-shot measurement for magnons.

Demonstrated a proof-of-principle quantum sensor for magnon detection.

Abstract

The recent development of hybrid systems based on superconducting circuits has opened up the possibility of engineering sensors of quanta of different degrees of freedom. Quantum magnonics, which aims to control and read out quanta of collective spin excitations in magnetically-ordered systems, furthermore provides unique opportunities for advances in both the study of magnetism and the development of quantum technologies. Using a superconducting qubit as a quantum sensor, we report the detection of a single magnon in a millimeter-sized ferromagnetic crystal with a quantum efficiency of up to~$0.71$. The detection is based on the entanglement between a magnetostatic mode and the qubit, followed by a single-shot measurement of the qubit state. This proof-of-principle experiment establishes the single-photon detector counterpart for magnonics.