Floquet Spin Amplification

TL;DR

This paper demonstrates magnetic-field signal amplification using periodically driven $^{129}$Xe spins, revealing a new Floquet amplification mechanism that enhances measurement sensitivity to femtotesla levels.

Contribution

It introduces the concept of Floquet amplification in quantum spin systems, extending quantum amplification physics to periodically driven (Floquet) systems.

Findings

Observed signal amplification at Floquet spin transition frequencies

Achieved at least tenfold improvement in magnetic field measurement sensitivity

Extended quantum amplification principles to Floquet systems

Abstract

Detection of weak electromagnetic waves and hypothetical particles aided by quantum amplification is important for fundamental physics and applications. However, demonstrations of quantum amplification are still limited; in particular, the physics of quantum amplification is not fully explored in periodically driven (Floquet) systems, which are generally defined by time-periodic Hamiltonians and enable observation of many exotic quantum phenomena such as time crystals. Here we investigate the magnetic-field signal amplification by periodically driven $^{129}$Xe spins and observe signal amplification at frequencies of transitions between Floquet spin states. This "Floquet amplification" allows to simultaneously enhance and measure multiple magnetic fields with at least one order of magnitude improvement, offering the capability of femtotesla-level measurements. Our findings extend the physics of quantum amplification to Floquet systems and can be generalized to a wide variety of existing amplifiers, enabling a previously unexplored class of "Floquet amplifiers".