Squeezed states of magnons and phonons in cavity magnomechanics

Abstract

We show how to create quantum squeezed states of magnons and phonons in a cavity magnomechanical system. The magnons are embodied by a collective motion of a large number of spins in a macroscopic ferrimagnet, and couple to cavity microwave photons and phonons (vibrational modes of the ferrimagnet) via the magnetic dipole interaction and magnetostrictive interaction, respectively. The cavity is driven by a weak squeezed vacuum field generated by a flux-driven Josephson parametric amplifier, which is essential to get squeezed states of the magnons and phonons. We show that the magnons can be prepared in a squeezed state via the cavity-magnon beamsplitter interaction, and by further driving the magnon mode with a strong red-detuned microwave field, the phonons are squeezed. We show optimal parameter regimes for obtaining large squeezing of the magnons and phonons, which are robust against temperature and could be realized with experimentally reachable parameters.

Entangling two magnon modes via magnetostrictive interaction

“…This is confirmed by figure 2(a) and it manifests that the optimal situation is that the magnon mode is resonant with the cavity, Δ 2 ; Δ a ; −ω b (see figure 1(c)). This is also the case for generating squeezed states of magnons by driving the cavity with a squeezed microwave field [21]. Figures 2(b) and (c) denote the cavity-magnon (m 1 ) entanglement E am 1 with g 2 =0 and the magnon-magnon entanglement E m m 1 2 with ¹ g 0 2 , respectively.…”

“…Cavity-magnon systems of YIG spheres provide also a promising and completely new platform for the study of macroscopic quantum states [14,21]. A magnon mode can get squeezed by driving the cavity with a squeezed vacuum microwave field, and the squeezing can further be transferred to the mechanical mode if the magnetostrictive interaction is activated by driving the magnon mode with a red-detuned microwave field [21]. Such a hybrid cavity magnomechanical system can also be prepared in a genuinely tripartite entangled state by suitably driving the YIG sphere and essentially utilizing the nonlinear magnetostrictive interaction [14].…”

“…Such a hybrid cavity magnomechanical system can also be prepared in a genuinely tripartite entangled state by suitably driving the YIG sphere and essentially utilizing the nonlinear magnetostrictive interaction [14]. Both the entangled and squeezed states of the magnon and mechanical modes are macroscopic quantum states due to a large size of the YIG sphere and an extremely large number of spins contained (more than 10 16 for a 250 μm diam YIG sphere that has been employed in [14,21]). Alternatively, nonclassical magnon states can be prepared by coupling magnons to a superconducting qubit which provides necessary nonlinearity [11,12].…”

Theory of quantum acoustomagnonics and acoustomechanics with a micromagnet

“…This is the dispersive magnon-phonon interaction employed so far in acoustomagnonics [20][21][22][23]. Note that, precisely because it stems from a second-order contribution, the corresponding interaction rates are small, usually in the ∼ 10mHz range for R ∼ 100 µm [20].…”

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.…”