Juan Torres Luna
TU Delft – Quantum Tinkerer group
Understanding the fate of the poor man’s Majorana in the long-chain limit
When: 12:00-13:00 CET, February 18th (Tuesday), 2025
Where: Sala de Seminarios (182), ICMM-CSIC, Campus de Cantoblanco, Madrid
The quality of topological qubits based on Majorana bound states (MBS) depends uniquely on two properties: the size of the topological gap and the MBS localization length. While the Kitaev model features perfectly localized MBS and a maximal gap, realistic systems exhibit finite localization length and the gap is limited by proximity effect, which raises the question of what platform can realise the best MBS. In this work, we study the quality of MBS in two platforms: the Lutchyn-Oreg (LO) model and the quantum dot chain model.
For the quantum dot chain, we find a trade-off between weak coupling—where the gap is small and the localization length is small—and the strong coupling regime—where the gap is large and the localization length is large. For the LO model, we find that the interplay between spin-orbit coupling and momentum yields a gap and localization length that cannot be simultaneously optimized. In order to find the best MBS that each model can achieve, we use multi-objective optimization to find the set of optimal localization lengths and gaps. We demonstrate that quantum dot chains can achieve MBS quality comparable to nanowire models, with extra tunability of the gap and localization. Our results highlight quantum dot chains as a versatile platform for high-quality MBS and topological quantum computing.