# Robust electric dipole transition at microwave frequencies for nuclear spin qubits in silicon

## TL;DR

This paper demonstrates how to induce a strong electric dipole in silicon-based nuclear spin qubits, enabling robust coupling to microwave resonators and other spins, thus advancing solid-state quantum information processing.

## Contribution

It introduces a method to generate a strong electric dipole at microwave frequencies for nuclear spins in silicon, enhancing their coupling capabilities for quantum applications.

## Key findings

- Achieved >100 Debye electric dipole at microwave frequencies.
- Long dephasing times (>1 ms) due to insensitivity to electrical noise.
- Enabled strong coupling to microwave resonators and nuclear spins.

## Abstract

The nuclear spin state of a phosphorus donor ($^{31}$P) in isotopically enriched silicon-28 is an excellent host to store quantum information in the solid state. The spin's insensitivity to electric fields yields a solid-state qubit with record coherence times, but also renders coupling to other quantum systems very challenging. Here, we describe how to generate a strong electric dipole ($>100$ Debye) at microwave frequencies for the nuclear spin. This is achieved by applying a magnetic drive to the spin of the donor-bound electron, while simultaneously controlling its charge state with electric fields. Under certain conditions, the microwave magnetic drive also renders the nuclear spin resonance frequency and electric dipole strongly insensitive to electrical noise, yielding long ($>1$ ms) dephasing times and robust gate operations. The nuclear spin could then be strongly coupled to microwave resonators, with a vacuum Rabi splitting of order 1 MHz, or to other nuclear spins, nearly half a micrometer apart, via strong electric dipole-dipole interaction. This work brings the $^{31}$P nuclear qubit into the realm of hybrid quantum systems and opens up new avenues in quantum information processing.