A research team at QuTech has successfully created a three-site Kitaev chain using semiconducting quantum dots connected by superconducting segments in a hybrid InSb/Al nanowire. This significant advancement, published in Nature Nanotechnology, demonstrates that extending the chain from two to three sites increases the stability of zero-energy modes, suggesting a path toward practical quantum computing applications.
Majorana Zero Modes (MZMs) are specialized quasiparticles that appear at the edges of topological superconductors. These particles are particularly valuable for quantum computing due to their non-Abelian exchange statistics, which could enable decoherence-free quantum computation and high-fidelity quantum gates.
The Kitaev model creates a one-dimensional topological superconductor by chaining spinless fermions with p-wave superconductivity and electron hopping. Previous work by the same team had demonstrated a minimal two-site chain hosting MZMs, though these suffered from low stability and were dubbed “poor man’s MZMs.” The current research expands this to three sites, showing improved stability.
Led by Leo Kouwenhoven and Grzegorz Mazur, with first authors Alberto Bordin and Chun-Xiao Liu, the team built on earlier foundational work. They combined their previous research on triplet Cooper pair splitting, two-site chain fabrication, and system tuning to create a more sophisticated device with eleven gates.
The researchers observed remarkable reproducibility across multiple devices, confirming that three-site chains consistently display enhanced robustness against perturbations. According to their calculations, chains of five or six sites could provide sufficient stability to outperform other approaches to quantum computing.
Looking ahead, the team plans to investigate how these Kitaev chains function as qubits and how chain length affects qubit lifetime. They’re exploring machine learning for automatic tuning of longer chains to achieve true topological protection. Additional research on three-site Kitaev chains coupled to quantum dots is already underway, continuing their methodical progress toward developing a practical topological qubit.
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