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arXiv:2411.18512 · Physical review. B./Physical review. B

Second-order correlation and squeezing of photons in cavities with ultrastrong magnon-photon interactions

Vemund Falch, Arne Brataas, Alireza Qaiumzadeh

Published Mar 18, 2025• 6 citations
arXivHTMLPDF

Abstract

We investigate the second-order photon correlation function in cavity-magnon systems, focusing on ferromagnetic and antiferromagnetic cavities within the ultrastrong coupling regime, and extending beyond the rotating-wave approximation. By deriving exact integral solutions for the second-order correlation function, we demonstrate that counter-rotating magnon-photon interactions induce quadrature squeezing in the cavity mode. Furthermore, we show that tuning the anisotropic magnon-cavity couplings enhances the squeezing effect by changing the level repulsion of the magnon-cavity photon hybrid mode without increasing the cavity photon occupation number. Our study reveals distinct quantum correlation behaviors in ferromagnetic and antiferromagnetic cavities: For ferromagnetic cavities, we show that squeezing increases with coupling strength asymmetry, whereas in the antiferromagnetic case, magnon modes with opposite chirality suppress quantum effects and impose a lower bound on correlation functions. These findings provide a pathway to optimize photon blockade for quantum information technology in magnon-cavity systems in the ultrastrong coupling limit.

DOI
10.1103/physrevb.111.104425

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Abstract A scheme that harnesses magnon squeezing under weak pump driving within a cavity magnomechanical system to achieve a robust magnon (photon) blockade is proposed. Through meticulous analytical calculations of optimal parametric gain and detuning values, the objective is to enhance the second‐order correlation function. The findings demonstrate a substantial magnon blockade effect under ideal conditions, accompanied by a simultaneous photon blockade effect. Impressively, both numerical and analytical results are found to be in complete accord, providing robust validation for the consistency of the findings. It is anticipated that the proposed scheme will serve as a pioneering approach toward the practical realization of magnon (photon) blockade in experimental cavity magnomechanical systems.
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The antibunching effect generated in a cavity containing first a single two-level atomic system and then two identical atoms is explored for off-resonant interactions, in strong- and weak-coupling regimes. The cavity is driven by coherent and squeezed sources. Using the second-order correlation function analytically derived in the weak-excitation regime, we show that squeezed light achieves and improves strong antibunching, leading to a photon blockade. This enhancement is due to a destructive quantum interference mechanism induced by the nonclassical light, creating a supplementary transition pathway. The best effect is obtained for equal frequency detunings in the strong-coupling regime. More interestingly, our investigation reveals that the two-atom-cavity system can further improve the antibunching effect compared to the single-atom cavity. It turns out that the additional couplings appearing in the cavity due to the implementation of the two atoms, combined with the squeezed light, could substantially enhance the photon-blockade effect.