# Multi-frequency Spin Manipulation Using Rapidly Tunable Superconducting Coplanar Waveguide Microresonators

## TL;DR

This paper presents superconducting NbTiN coplanar waveguide microresonators with rapid frequency tunability for multi-frequency pulsed ESR, enabling advanced spin manipulation and potential quantum memory applications.

## Contribution

Introduction of a frequency-tunable superconducting microresonator capable of rapid, continuous tuning for multi-frequency ESR experiments with demonstrated spin control.

## Key findings

- Resonance frequency tunable by 95 MHz in 270 ns without quality factor loss.
- Successful manipulation of phosphorus and arsenic spins in a single pulse sequence.
- Effective use of adiabatic pulses to overcome inhomogeneities and power limitations.

## Abstract

In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency ($\sim$7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance (DEER). Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.