# Defects in Silicon Carbide as Quantum Qubits: Recent Advances in Defect Engineering
## 2 Quantum Qubits
However, challenges remain in improving coupling efficiency and achieving high-fidelity gate operations [35; 36];
* Topological Qubits: Topological qubits are based on anyonic excitations in topologically ordered materials, such as Majorana fermions in topological superconductors. The materials under investigation include superconducting nanowires made of InAs or MoTe\({}_{2}\). These qubits are robust to local noise and decoherence due to their topological nature, offering the potential for long-lived qubits. However, this platform is still experimental, and significant challenges remain in achieving reliable and scalable topological qubit systems [37; 38]. Table 1 provides a summary of the main advantages and challenges with all the physical systems mentioned above. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Type** & **Advantages** & **Challenges** \\ \hline \multirow{6}{*}{Superconducting qubits} & Well-established & \multirow{2}{*}{Short coherence times (microseconds) and require cryogenic cooling.} \\  & fabrication processes, strong control and readout capabilities, and compatibility with microwave technology. & \multirow{2}{*}{Slow gate speeds, complex laser-based control, and scalability challenges.} \\  & & \\ \cline{1-1}  & Long coherence times (seconds) and high-fidelity gate operations. & \multirow{2}{*}{Slow gate speeds, complex laser-based control, and scalability challenges.} \\ \cline{1-1}  & Compatible with CMOS & \multirow{2}{*}{Requires precise nanofabrication and challenging control of qubit interactions.} \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \hline \multirow{6}{*}{Topological qubits} & Theoretically fault tolerant and protected & \multirow{2}{*}{Experimentally unconfirmed and complex fabrication requirements.} \\  & from decoherence. & & \\ \cline{1-1} \cline{2-2} \cline{4-4}  & Optical addressability, long coherence times, and potential for room-temperature operation. & \multirow{2}{*}{Difficult to create and control defects with high precision.} \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Different quantum qubit platforms, with their main advantages and challenges [22; 23; 24; 39]. It should be noted that the list of material platforms in Table 1 is not exhaustive. Other platforms, such as photonic qubits [40], are actively being investigated, and new candidates continue to emerge as research in the field advances. With this in mind, we focus on defect-based qubits in SiC. The first fundamental question to address is as follows: What makes a defect a viable candidate for a quantum qubit? A key reference in answering this question is the pioneering work by [PERSON] et al. [4], which established a well-defined set of criteria for defect-based qubits. This work outlines essential properties that both the defect and the host material must satisfy to function as a quantum qubit. A summary of these criteria is presented in Table 2.