# Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies

## TL;DR

This paper demonstrates GHz-frequency control of a single phosphorus atom in silicon using an epitaxial transistor, revealing excited states and relaxation dynamics crucial for quantum computing applications.

## Contribution

It provides the first systematic investigation of rf excitation effects on a single atom transistor, including excited state identification and relaxation rate measurement.

## Key findings

- Excited state at approximately 9 meV consistent with a phosphorus donor
- Relaxation rate of the excited state exceeds 2.5 GHz
- Successful GHz-frequency control of a single atom transistor

## Abstract

The ability to apply GHz frequencies to control the quantum state of a single $P$ atom is an essential requirement for the fast gate pulsing needed for qubit control in donor based silicon quantum computation. Here we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to $\approx$ 13 GHz to heavily phosphorous doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy $\approx$ 9 meV consistent with the first excited state of a single $P$ donor in silicon. The relaxation rate of this first excited state to ground is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under rf excitations.