Instabilities near Ultrastrong Coupling in a Microwave Optomechanical Cavity

Abstract

With artificially engineered systems, it is now possible to realize the coherent interaction rate, which can become comparable to the mode frequencies, a regime known as ultrastrong coupling (USC). We experimentally realize a cavity-electromechanical device using a superconducting waveguide cavity and a mechanical resonator. In the presence of a strong pump, the mechanical-polaritons splitting can nearly reach 81% of the mechanical frequency, overwhelming all the dissipation rates. Approaching the USC limit, the steady-state response becomes unstable. We systematically measure the boundary of the unstable response while varying the pump parameters. The unstable dynamics display rich phases, such as selfinduced oscillations, period-doubling bifurcation, and period-tripling oscillations, ultimately leading to the chaotic behavior. The experimental results and their theoretical modeling suggest the importance of residual nonlinear interaction terms in the weak-dissipative regime.

Instability of multi-mode systems with quadratic Hamiltonians

“…More precisely, the squeezing term of Hamiltonian triggers the instability in optomechanical systems. The effect is not solely determined by the type of detuning alone: The system can become unstable in the red-detuning regime [as shown in cases (2) and (3), illustrated in figure 2(a), which was experimentally demonstrated in a very recent work [25]], whereas it can be controlled stable in the blue-detuning regime [case (5), figure 2(b)]. Figure 2(a) shows that the average numbers diverge of the cavity and mechanical modes when the cavity is driven by a red-detuned laser with Δ = 1.5Ω > 0.…”

Preparation of Distant Quantum Entanglement and One‐way Quantum Steering in Hybrid Cavity‐Magnonics‐and‐Cavity‐Optomechanical Systems

“…In our study, the parameters we use below are mainly chosen from the following experimental literature. [ 54–59 ] In order to neglect the Kerr properties of magnons, it is necessary to choose a YIG sphere with a sufficiently large diameter. In this case, we selected a diameter of approximately 250 m and a density of $$\rho = 4.22 \times 10^{27}$$ $$\text{m}^{-3}$$ for the YIG sphere.…”