Excitation and coherent control of spin qudit modes with sub-MHz spectral resolution

TL;DR

This paper demonstrates excitation and control of spin qudit modes in silicon carbide with sub-MHz spectral resolution at room temperature, enabling advanced quantum sensing applications.

Contribution

It introduces a two-frequency protocol for manipulating spin qudits in SiC, achieving narrow spectral widths and high spectral resolution under ambient conditions.

Findings

Spectral width of qudit modes is an order of magnitude narrower than inhomogeneous broadening.

Achieved spectral selectivity of 600 kHz and resolution of 30 kHz using Ramsey interferometry.

Demonstrated absolute DC magnetometry insensitive to thermal noise and strain fluctuations.

Abstract

Quantum bit or qubit is a two-level system, which builds the foundation for quantum computation, simulation, communication and sensing. Quantum states of higher dimension, i.e., qutrits (D = 3) and especially qudits (D = 4 or higher), offer significant advantages. Particularly, they can provide noise-resistant quantum cryptography, simplify quantum logic and improve quantum metrology. Flying and solid-state qudits have been implemented on the basis of photonic chips and superconducting circuits, respectively. However, there is still a lack of room-temperature qudits with long coherence time and high spectral resolution. The silicon vacancy centers in silicon carbide (SiC) with spin S = 3/2 are quite promising in this respect, but until now they were treated as a canonical qubit system. Here, we apply a two-frequency protocol to excite and image multiple qudit modes in a SiC spin ensemble under ambient conditions. Strikingly, their spectral width is about one order of magnitude narrower than the inhomogeneous broadening of the corresponding spin resonance. By applying Ramsey interferometry to these spin qudits, we achieve a spectral selectivity of 600 kHz and a spectral resolution of 30 kHz. As a practical consequence, we demonstrate absolute DC magnetometry insensitive to thermal noise and strain fluctuations.