Variable bandwidth, high efficiency microwave resonator for control of spin-qubits in nitrogen-vacancy centers

TL;DR

This paper introduces a variable bandwidth microwave resonator optimized for controlling nitrogen-vacancy centers in diamond, enabling efficient spin manipulation with high power-to-field conversion and tunable frequency for advanced quantum experiments.

Contribution

The work presents a novel planar microwave resonator design with high efficiency, tunability, and homogeneous magnetic field generation for NV-center spin control.

Findings

Operates at 2.9 GHz with 1000 MHz bandwidth in transmission mode.

Produces $$-pulses of 50 ns with only 200 mW power.

Tunable between 1.3 GHz and 6 GHz for different magnetic field conditions.

Abstract

Nitrogen-Vacancy (NV) centers in diamond are attractive tools for sensing and quantum information. Realization of this potential requires effective tools for controlling the spin degree of freedom by microwave (mw) magnetic fields. In this work we present a planar microwave resonator optimized for microwave-optical double resonance experiments on single nitrogen-vacancy (NV) centers in diamond. It consists of a piece of wide microstrip line which is symmetrically connected to two 50 $\Omega$ microstrip feed lines. In the center of the resonator, an $\Omega$-shaped loop focuses the current and the mw magnetic field. It generates a relatively homogeneous magnetic field over a volume of 0.07mm$^2\times$0.1mm. It can be operated at 2.9 GHz in both transmission and reflection modes with bandwidths of 1000 MHz and 400 MHz, respectively. The high power-to-magnetic field conversion efficiency allows to produce $\pi$-pulses with a duration of 50 ns with only about 200 mW and 50 mW microwave power in transmission and reflection, respectively. The transmission mode also offers capability for efficient radio frequency excitation. The resonance frequency can be tuned between 1.3 GHz and 6 GHz by adjusting the length of the resonator. This will be useful for experiments on NV-centers at higher external magnetic fields and on different types of optically active spin centers.