Steady Bell State Generation via Magnon-Photon Coupling

Abstract

We show that parity-time (PT ) symmetry can be spontaneously broken in the recently reported energy level attraction of magnons and cavity photons. In the PT -broken phase, magnon and photon form a high-fidelity Bell state with maximum entanglement. This entanglement is steady and robust against the perturbation of environment, in contrast to the general wisdom that expects instability of the hybridized state when the symmetry is broken. This anomaly is further understood by the compete of non-Hermitian evolution and particle number conservation of the hybridized system. As a comparison, neither PT -symmetry broken nor steady magnon-photon entanglement is observed inside the normal level repulsion case. Our results may open a novel window to utilize magnonphoton entanglement as a resource for quantum technologies.

Introducing coherent time control to cavity magnon-polariton modes

“…Spectroscopic two-tone experiments predicted and observed the regime of level attraction [14,17,28], which has also been linked to an entanglement of photon and magnon [29]. Our technique would allow to prepare the CMP in this regime and then observe its time-evolution.…”

Enhanced entanglement and asymmetric EPR steering between magnons

“…Hybrid magnonical systems have become a promising platform in the study of the macroscopic quantum phenomenon due to the large size of the magnon systems. Recently, several schemes have been proposed to generate different types of quantum correlations between magnons and photons or phonons [36][37][38][39]. However, whether asymmetric EPR steering can be achieved in such hybrid systems is still unknown.…”

Magnon blockade in a hybrid ferromagnet-superconductor quantum system

“…Magnon, regarded as the quantized spin wave, is the dynamic intrinsic excitation of the magnetic ordered body [10], which has been the subject of extensive investigations in many fields of research, for instance, cavity optomagnonics [11][12][13], hybrid ferromagnetic-superconducting system [14][15][16][17], and Dirac or Weyl magnons in topological insulators [18][19][20]. Many novel phenomena and important applications, ranging from optical cooling of magnon [21] and magnon-induced high-order sideband generation [22][23][24] to magnon gradient memory [25,26] and observation of topological magnon insulator states [27] have been theoretically or experimentally verified.Recently, the investigation of the quantum characteristics of the magnon-polariton system has fascinated widespread concern and made substantial progress [28][29][30][31][32]. For example, the generations of magnon-photon-phonon entanglement [28] and squeezed magnon-phonon states [31] from the cavity magnomechanics, as well as the steady Bell state generation via magnon-photon coupling [32] have been proposed.…”

“…Many novel phenomena and important applications, ranging from optical cooling of magnon [21] and magnon-induced high-order sideband generation [22][23][24] to magnon gradient memory [25,26] and observation of topological magnon insulator states [27] have been theoretically or experimentally verified.Recently, the investigation of the quantum characteristics of the magnon-polariton system has fascinated widespread concern and made substantial progress [28][29][30][31][32]. For example, the generations of magnon-photon-phonon entanglement [28] and squeezed magnon-phonon states [31] from the cavity magnomechanics, as well as the steady Bell state generation via magnon-photon coupling [32] have been proposed. However, as a typical pure quantum phenomenon, the magnon blockade is still unexplored.…”

“…Recently, the investigation of the quantum characteristics of the magnon-polariton system has fascinated widespread concern and made substantial progress [28][29][30][31][32]. For example, the generations of magnon-photon-phonon entanglement [28] and squeezed magnon-phonon states [31] from the cavity magnomechanics, as well as the steady Bell state generation via magnon-photon coupling [32] have been proposed. However, as a typical pure quantum phenomenon, the magnon blockade is still unexplored.…”