# Asymmetric quantum shot noise in magnon transport

## TL;DR

This paper investigates the quantum properties of magnon transport in ferromagnetic insulators by analyzing frequency-dependent noise ratios, revealing quantum shot noise phenomena and their experimental accessibility at low temperatures.

## Contribution

It introduces the concept of asymmetric quantum shot noise in magnon transport and demonstrates its increase with frequency, breaking classical noise limits.

## Key findings

- Noncommutative noise increases monotonically with frequency.
- Quantum shot noise breaks classical noise bounds.
- Predictions are experimentally accessible with current technology.

## Abstract

We study a frequency-dependent noise-to-current ratio for asymmetric, symmetric, and noncommutative current-noise in a ferromagnetic insulating junction, and extract quantum-mechanical properties of magnon transport at low temperatures. We demonstrate that the noncommutative noise, vanished in the dc-limit (i.e., a classical regime), increases monotonically as a function of frequency, and show that the noncommutative noise associated directly with quantum fluctuations of magnon currents breaks through the classical upper limit determined by the symmetric noise and realizes asymmetric quantum shot noise. Finally, we show that our theoretical predictions are within experimental reach with current device and measurement scheme while exploiting low temperatures. Our work provides a platform toward experimental access to quantum fluctuations of magnon currents.