Nonlinearities in mechanical resonators approaching the quantum regime

Adrian Bachtold, ICFO

Barcelona, Spain

May 28, 14h00     D207

An open question in mechanics is whether mechanical resonators can be made nonlinear with vibrations approaching the quantum ground state. This requires engineering a mechanical nonlinearity far beyond what has been realized thus far. In this talk, I will present a mechanism to boost the Duffing (also called Kerr) nonlinearity by coupling the vibrations of a nanotube resonator to single-electron tunneling in a quantum dot and by operating the system in the ultrastrong coupling regime [1]. Remarkably, thermal vibrations become highly nonlinear when lowering the temperature. In a second series of experiments, we couple the nanotube vibrations and a double quantum dot qubit, which is readout with a superconducting resonator, enabling us to observe nonlinear vibrations at the zero-point motion level. Our work paves the way for realizing mechanical qubits [2], quantum simulators emulating the electron-phonon coupling, and macroscopic quantum superposition states [3].

Figure 1 – Electromechanical device consisting of a double-quantum dot (in red) video controlsded in a suspended carbon nanotube clamped at its two ends. The double-quantum dot is defined by electrostatics means using the five gate electrodes. For the readout, the electromechanical device is dispersively coupled to a superconducting resonator

[1] C. Samanta, S. L. De Bonis, C. B. Møller, R. Tormo-Queralt, W. Yang, C. Urgell, B. Stamenic, B. Thibeault, Y. Jin, D. A. Czaplewski, F. Pistolesi, A. Bachtold, Nature Physics 19, 1340 (2023)

[2] F. Pistolesi, A. N. Cleland, A. Bachtold, Phys. Rev. X 11, 031027 (2021)

[3] M. Roda-Llordes, A. Riera-Campeny, D. Candoli, P. T. Grochowski, O. Romero-Isart, Phys. Rev. Lett. 132, 023601 (2023)