Finite time St\"uckelberg interferometry with nanomechanical modes

TL;DR

This paper investigates finite time effects in St"uckelberg interferometry using a classical nanomechanical system, providing an exact analytical solution and exploring new parameter regimes with experimental validation.

Contribution

It offers an exact analytical solution to the St"uckelberg problem and experimentally explores uncharted parameter regimes in a classical nanomechanical system.

Findings

Identified new parameter regimes of St"uckelberg interferometry.

Demonstrated excitation oscillations without crossing the avoided crossing.

Provided a theoretical framework applicable to quantum two-level systems.

Abstract

St\"uckelberg interferometry describes the interference of two strongly coupled modes during a double passage through an avoided energy level crossing. In this work, we experimentally investigate finite time effects in St\"uckelberg interference and provide an exact analytical solution of the St\"uckelberg problem. Approximating this solution in distinct limits reveals uncharted parameter regimes of St\"uckelberg interferometry. Experimentally, we study these regimes using a purely classical, strongly coupled nanomechanical two-mode system of high quality factor. The classical two-mode system consists of the in-plane and out-of-plane fundamental flexural mode of a high stress silicon nitride string resonator, coupled via electric gradient fields. The dielectric control and microwave cavity enhanced universal transduction of the nanoelectromechanical system allows for the experimental access to all theoretically predicted St\"uckelberg parameter regimes. We exploit our experimental and theoretical findings by studying the onset of St\"uckelberg interference in dependence of the characteristic system control parameters and obtain characteristic excitation oscillations between the two modes even without the explicit need of traversing the avoided crossing. The presented theory is not limited to classical mechanical two-mode systems but can be applied to every strongly coupled (quantum) two-level system, for example a spin-1/2 system or superconducting qubit.