Abstract
Hybrid quantum devices expand the tools and techniques available for quantum sensing in various fields. Here, we experimentally demonstrate quantum sensing of a steady-state magnon population in a magnetostatic mode of a ferrimagnetic crystal. Dispersively coupling the magnetostatic mode to a superconducting qubit allows for the detection of magnons using Ramsey interferometry with a sensitivity on the order of 10^{-3} magnons/sqrt[Hz]. The protocol is based on dissipation as dephasing via fluctuations in the magnetostatic mode reduces the qubit coherence proportionally to the number of magnons.
Highlights
Hybrid quantum devices expand the tools and techniques available for quantum sensing in various fields
We experimentally demonstrate quantum sensing of a steady-state magnon population in a magnetostatic mode of a ferrimagnetic crystal
Quantum states are intrinsically fragile with regards to external perturbations. This property is leveraged in quantum sensing, where appropriate quantum systems can be monitored to detect a signal [1]
Summary
Hybrid quantum devices expand the tools and techniques available for quantum sensing in various fields. (d) Magnon detection sensitivity S calculated as a function of the Kittel mode linewidth γm=2π, for amplitudes of the qubit–magnon dispersive shift jχq−mj=2π 1⁄4 2 MHz (solid line) and 10 MHz (dashed line). Measuring the qubit state yields different results depending on the number of magnons present in the Kittel mode.
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