Ground State Cooling in a Hybrid Ferro-Magnet-Superconducting System Coupled with Mechanical Resonators

Lin Tian

Claudia P. Cortés, Matthew Otten, Stephen K. Gray

Roson Nongthombam, Ambaresh Sahoo, Amarendra K. Sarma

We present a scheme for ground-state cooling of a mechanical resonator by simultaneously coupling it to a superconducting qubit and a cavity field. The Hamiltonian describing the hybrid system dynamics is systematically derived. The cooling process is driven by a red-detuned ac drive on the qubit and a laser drive on the optomechanical cavity. We have investigated cooling in the weak and the strong coupling regimes for both the individual system, i.e., qubit assisted cooling and optomechanical cooling, and compared them with the effective hybrid cooling. We show that in the weak coupling and resolved sideband regime, cooling is more efficient in the hybrid case for a specific choice of parameters. On the other hand, in the strong coupling, the hybrid cooling is found to be more effective compared to the individual cooling mechanisms in the resolved regimes.

Sourav Majumder, Tanmoy Bera, Vibhor Singh

Hybrid devices based on the superconducting qubits have emerged as a promising platform for controlling the quantum states of macroscopic resonators. The nonlinearity added by a qubit can be a valuable resource for such control. Here we study a hybrid system consisting of a mechanical resonator longitudinally coupled to a transmon qubit. The qubit readout can be done by coupling to a readout mode like in c-QED setup. The coupling between the mechanical resonator and transmon qubit can be implemented by the modulation of the superconducting quantum interference device inductance. In such a tripartite system, we analyze the steady-state occupation of the mechanical mode when all three modes are dispersively coupled. We use the quantum noise and the Lindblad formalism to show that the sideband cooling of the mechanical mode to its ground state is achievable. We further experimentally demonstrate that measurements of the thermomechanical motion are possible in the dispersive limit, while maintaining a large coupling between qubit and mechanical mode. Our theoretical calculations suggest that single-photon strong coupling is within the experimental reach in such hybrid devices.

Le-Tian Zhu, Xingyu Zhu, Guang-Can Guo +2 more

Daniel Huertas‐Hernando