Slit-loaded coplanar waveguide for color-center spin qubits

TL;DR

This paper introduces a compact slit-loaded coplanar waveguide that enables effective laser and microwave irradiation for controlling color-center spin qubits, facilitating integration into small-scale quantum devices.

Contribution

The study demonstrates a novel slit-loaded coplanar waveguide design that allows simultaneous laser and microwave access for spin control of color centers in a compact form factor.

Findings

Effective spin control of silicon vacancies in SiC achieved

Microwave magnetic fields persist after slit loading, enabling surface-oriented spin manipulation

Design is suitable for integration into semiconductor quantum sensors

Abstract

The spin qubits of color centers are extensively investigated for quantum sensing, communication, and information processing, with their states generally controlled using lasers and microwaves. However, it is challenging to effectively irradiate both lasers and microwaves onto color centers using small footprint microwave waveguides or antennas that are compatible with semiconductor devices. We experimentally show that by introducing a compact coplanar waveguide with a thin slit in its signal line, effective irradiation of both lasers and microwaves is enabled, allowing spin-state control of color centers created around the slit. Microwave magnetic fields parallel to the surface, intrinsically generated by a standard coplanar waveguide, persist even after loading the slit, which is necessary to control the color centers whose spin quantization axes are oriented perpendicular to the surface, while laser light for the initialization and readout of spin states can access the color centers through the slit. Continuous and pulsed optically detected magnetic resonance measurements are performed for the silicon vacancies ($\mathrm{V_{Si}}$) in silicon carbide 4H-SiC(0001). Experimental results indicate that the spin states of $\mathrm{V_{Si}}$ are effectively controlled by the microwave magnetic fields parallel to the surface, which agrees with numerical results from electromagnetic field simulations. Our small footprint waveguide is suitable for integrating color-center-based quantum sensors into semiconductor electronic devices and other small-scale systems.