Nonlinear nanomechanical resonators approaching the quantum ground state

TL;DR

This paper demonstrates a method to significantly enhance the nonlinearity of nanomechanical resonators by coupling them to single-electron tunneling, enabling vibrations near the quantum ground state and opening pathways for quantum state engineering.

Contribution

We introduce a mechanism to amplify Duffing nonlinearity in nanotube resonators via ultrastrong coupling to single-electron tunneling, achieving highly nonlinear thermal vibrations at low temperatures.

Findings

Thermal vibrations become highly nonlinear at low temperatures.

Average vibration amplitude reaches 13 times the zero-point motion.

Approximately 42% of thermal energy is stored in anharmonic potential.

Abstract

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. Here we discovered a mechanism to boost the Duffing nonlinearity by coupling the vibrations of a nanotube resonator to single-electron tunneling and by operating the system in the ultrastrong coupling regime. Remarkably, thermal vibrations become highly nonlinear when lowering the temperature. The average vibration amplitude at the lowest temperature is 13 times the zero-point motion, with approximately 42% of the thermal energy stored in the anharmonic part of the potential. Our work paves the way for realizing mechanical Schrodinger cat states [1], mechanical qubits [2, 3], and quantum simulators emulating the electron-phonon coupling [4].