Probabilistic motional averaging

TL;DR

This paper investigates how a qubit coupled to a resonator exhibits motional averaging under continuous measurement and external driving, revealing the interplay of driving strength, dissipation, and linewidth through experiments and theory.

Contribution

It provides a detailed analysis of motional averaging in a driven quantum system, combining experimental results with numerical and analytical models.

Findings

Transmission depends on driving strength, dissipation, and linewidth.

Experimental results agree with theoretical predictions.

Strong driving leads to a single averaged response.

Abstract

In a continuous measurement scheme a spin-1/2 particle can be measured and simultaneously driven by an external resonant signal. When the driving is weak, it does not prevent the particle wave-function from collapsing and a detector randomly outputs two responses corresponding to the states of the particle. In contrast, when driving is strong, the detector returns a single response corresponding to the mean of the two single-state responses. This situation is similar to a motional averaging, observed in nuclear magnetic resonance spectroscopy. We study such quantum system, being periodically driven and probed, which consists of a qubit coupled to a quantum resonator. It is demonstrated that the transmission through the resonator is defined by the interplay between driving strength, qubit dissipation, and resonator linewidth. We demonstrate that our experimental results are in good agreement with numerical and analytical calculations.