Intensive Cavity-Magnomechanical Cooling of a Levitated Macromagnet.

We describe microwave cavity-magnomechanical center-of-mass cooling of a levitated magnetic sphere. The standing magnetic component of the electromagnetic wave within a microwave cavity exerts a dynamical force on a magnonic crystalline sphere and dissipates the mechanical energy through scattering into the magnon mode. The coupling is established by the magnetic dipole interaction and enriched by the collective spin motion. We find that the final cooled phonon occupation achieved is an intensive property independent of the mass and size of the sphere, in contrast to standard optomechanical couplings. This is of particular importance for testing quantum mechanics with macroscopic objects.

Magnonic Einstein-de Haas Effect: Ultrafast Rotation of Magnonic Microspheres.

Magnons, collective spin excitations in magnetic crystals, have attracted much interest due to their ability to couple strongly to microwaves and other quantum systems. In compact magnetic crystals, we show that there are magnonic modes that can support orbital angular momentum and that these modes can be driven by linearly polarized microwave fields. Because of conservation of angular momentum, exciting such magnon modes induces a mechanical torque on the crystal. We study a levitated magnetic crystal, a yttrium iron garnet (YIG) microsphere, where such orbital angular momentum magnon modes are driven by microwaves held in a microwave high-Q microwave cavity. We find that the YIG sphere experiences a mechanical torque and can be spun up to ultralarge angular speeds exceeding 10 GHz.

Harnessing quantum superposition and interference in atomic systems.

We propose resilient quantum superposition states in closed-loop multilevel system which result in myriad quantum interference phenomena. An interplay of these superposition states results in a whole gamut of atomic phenomena including coherent population trapping (CPT), electromagnetically induced transparency (EIT), electromagnetically induced absorption (EIA), amplification without inversion (AWI) and enhancement of refractive index accompanied with negligible absorption. The polarization and the phases of the fields transform the underlying superposition of the excited states leading to all these effects, where, given the macroscopic nature of these phenomena the quantum superposition states as well as the synergy between them can be ascertained. Numerical simulations for D1 transition in room temperature Rb87 atomic vapour system bear out these findings.