Demonstration Of A Quantum Magnetometer Chip Based On Proprietary And Scalable 4H-Silicon Carbide Technology

TL;DR

The paper tackles the challenge of scalable, low-power quantum magnetometry by integrating V2 silicon-vacancy centers in a monolithic 4H-SiC planar waveguide. It employs wafer-scale fabrication with depth-controlled proton/electron implantation to create a high-density ensemble (≈$6.4\times10^7$ centers) and demonstrates a $916\,\mathrm{nm}$ zero-phonon line with efficient optical coupling. CW-ODMR and pulsed sequences (Rabi, Ramsey, Hahn-echo) show coherent control of the large ensemble, achieving sensitivities of $\eta_{\mathrm{cw}} < 270\,\mathrm{nT}/\sqrt{\mathrm{Hz}}$ and $\eta_{\mathrm{pulsed}} < 30\,\mathrm{nT}/\sqrt{\mathrm{Hz}}$, with $T_2^* \approx 230\,\mathrm{ns}$ and $T_2 \approx 2.8\,\mathrm{\mu s}$, supported by a $10$-dimensional Lindblad model of the V2 dynamics. This work provides a foundation for wafer-scale, energy-efficient quantum sensing in SiC, leveraging a photonic architecture and fabrication flow compatible with mass production, and outlines a path toward scalable SiC-based quantum sensors rivaling diamond-based systems in practical deployment.

Abstract

This work presents an industrially scalable, power-efficient and high-performance quantum magnetometer chip based on proprietary 4H-silicon carbide (SiC) technology, leveraging wafer-scale fabrication techniques to optimize V2 silicon vacancy color centers for highly reproducible, industry-grade fabrication with precise control of depth and density. The integration of these color center ensembles into a planar silicon carbide waveguide enables efficient excitation of a large ensemble and simplifies fluorescence extraction compared to standard confocal methods. We report continuous-wave (CW) optically detected magnetic resonance measurements, complemented by Rabi, Ramsey, and Hahn-echo sequences, which demonstrate coherent capabilities of the large embedded ensemble of V2 centers. Based on the data, our device exhibits sensor shot-noise limited sensitivities 2-3 orders of magnitude lower compared to more complex confocal techniques. Collectively, these advancements simplify the quantum sensor architecture, enhance sensitivity, and streamline optical excitation and collection, thereby paving the way for the development of next-generation SiC-quantum sensing technologies.

Figures (4)

• Figure 1: Illustration of the sensor concept: The planar monolithic 4H-SiC waveguide is formed as sandwich structure consisting of a n++ doped substrate, an intrinsically doped core and a very thin layer of SiO2 on top. The V2 C3v-symmetry axis points perpendicular to the sensor plane, enabling efficient RF-excitation by a simple microstrip design as shown above or alternatively by a coil. On the right, a schematic of the 4H-SiC crystal structure is shown, with corresponding silicon vacancy color centers, V1 and V2.
• Figure 2: a) Calculated $B_{1}$ field distributions induced by a 70 MHz current parallel and orthogonal to the color center symmetry axis at a distance of 3µ m from the microstrip. b) Confocal scan of the chip cross section, revealing a ribbon of V2 emerging from the proton implantation peak and a corresponding CW optical detected magnetic resonance (ODMR) measurement, fitted with a Lorentzian. c) Simulated defect density distribution induced by protons implanted into 4H-SiC with 400 keV and 600 keV. d) 8 K low-temperature spectrum of the V2 ensemble clearly showing the zero-phonon line (ZPL) at 916 nm and its phononic sideband.
• Figure 3: a) Hybrid quantum model for describing both the ground-state coherently as well as the fluorescence dynamics of the V2. b) Block diagram of characterization setup for both continuous wave and pulsed measurements. c) CW-ODMR measurements performed on the V2 ensemble embedded into the planar waveguide for the case of B0=0, and B0=250 $\upmu \mathrm{T}$, fitted with a single and double Lorentzian respectively. d) T1 measurement on the V2 ensemble in the waveguide by initializing the system with a first laser pulse and then reading out the fluorescence with a second laser pulse separated by a time-delay $\tau$.
• Figure 4: Pulsed measurements performed on the V2 ensemble in the planar waveguide, consisting of $\pi/2$ or $\pi$ RF-pulses, free evolution times $\tau$ and laser initialization and readout pulses $L$: a) Rabi-oscillations for different $B$1 amplitudes fitted with exponentially decaying harmonic, b) Pulsed ODMR measurement for different amplitudes of $B$1, c) Ramsey sequence for a detuning of 0 and 5MHz fitted with a decaying exponential and an exponentially decaying harmonic for the case of detuning respectively, d) Hahn-echo sequence performed for two different phases of the $\pi/2$-pulse (x:top and y:bottom) fitted with a decaying exponential.