# Nonexponential decay of a giant artificial atom

## TL;DR

This paper experimentally demonstrates a giant artificial atom interacting with surface acoustic waves, revealing non-Markovian dynamics and nonexponential decay due to the atom's large size relative to the wavelength.

## Contribution

It introduces the giant atom regime in quantum acoustics, showing non-Markovian effects and nonexponential decay in a superconducting qubit coupled to surface acoustic waves.

## Key findings

- Observation of non-Markovian dynamics in giant atoms
- Detection of nonexponential relaxation behavior
- Frequency spectrum analysis confirming non-Markovian effects

## Abstract

In quantum optics, light-matter interaction has conventionally been studied using small atoms interacting with electromagnetic fields with wavelength several orders of magnitude larger than the atomic dimensions. In contrast, here we experimentally demonstrate the vastly different giant atom regime, where an artificial atom interacts with acoustic fields with wavelength several orders of magnitude smaller than the atomic dimensions. This is achieved by coupling a superconducting qubit to surface acoustic waves at two points with separation on the order of 100 wavelengths. This approach is comparable to controlling the radiation of an atom by attaching it to an antenna. The slow velocity of sound leads to a significant internal time-delay for the field to propagate across the giant atom, giving rise to non-Markovian dynamics. We demonstrate the non-Markovian character of the giant atom in the frequency spectrum as well as nonexponential relaxation in the time domain.