Stable spin squeezing of nitrogen-vacancy centers via Floquet-driven magnons

We propose an efficient scheme for generating a stable spin-squeezed state in a hybrid magnon-nitrogen-vacancy (NV) centers system via magnon-Floquet driving. The system consists of a yttrium iron garnet (YIG) film directly coupled to NV centers that are equidistant from the film surface, and at the same time the YIG film is driven by a Floquet field. The magnon dissipation is exploited to distribute the NV centers into the dark state, manifesting as the stable spin-squeezed state. We show that the system exhibits the low- or high-energy dark state, which is determined by whether the lowering or the raising spin operator plays the dominant role in evolution. Furthermore, we also show that the spin squeezing is robust against thermal effects and decoherence, and it is possible to detect the change in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>N</a:mi> </a:math> at the single-spin level, since it exhibits a distinct odd-even effect. This scheme provides a feasible way for experimental implementation and thus has potential applications in quantum information processing, quantum simulation, and precision metrology.