Orateur
Description
The promise of Majorana zero modes (MZMs) for fault-tolerant topological quantum computing stems from their unique non-Abelian statistics and inherent topological protection from local decoherence [1]. However, after fifteen years of research, distinguishing MZMs from near-zero-energy Andreev bound states (ABSs) in hybrid devices remains a key challenge. This “Majorana versus Andreev” challenge [2] has revealed that, rather than being a disadvantage,ABSs can serve as a foundation for novel qubit designs. One promising approach encodes a qubit in the spin of a quasiparticle residing in an ABS of a quantum dot [3]. Embedding such a superconducting spin qubit into a transmon circuit provides an intrinsic spin-supercurrent coupling, enabling an effective interface with circuit quantum electrodynamics for coherent control, readout, and strong qubit-qubit coupling [4]. Alternatively, a minimal Kitaev chain implemented in quantum dots coupled via superconductors [5] is a promising platform. Even a minimal chain of two dots can host a pair of Majorana modes and store quantum information in their joint parity. Recent quantum capacitance measurements on such platforms have enabled single-shot parity readout and demonstrated parity lifetimes exceeding 1 millisecond [6]. These results establish essential readout capabilities and resolve a long-standing experimental challenge, paving the way for time-domain control of Majorana-based qubits.
[1] Majorana qubits for topological quantum computing, Ramón Aguado, Leo P Kouwenhoven, Physics Today 73, 44 (2020).
[2] From Andreev to Majorana bound states in hybrid superconductor-semiconductor nanowires, Elsa Prada, Pablo San-Jose, Michiel WA de Moor, Attila Geresdi, Eduardo JH Lee, Jelena Klinovaja, Daniel Loss, Jesper Nygård, Ramón Aguado, Leo P Kouwenhoven, Nature Review Physics,2, 575–594 (2020).
[3] Spectroscopy of Spin-Split Andreev Levels in a Quantum Dot with Superconducting Leads, Arno Bargerbos, Marta Pita-Vidal, Rok Žitko, Lukas J Splitthoff, Lukas Grünhaupt, Jaap J Wesdorp, Yu Liu, Leo P Kouwenhoven, Ramón Aguado, Christian Kraglund Andersen, Angela Kou, Bernard Van Heck, Phys. Rev. Lett. 131, 097001 (2023)
[4] Direct manipulation of a superconducting spin qubit strongly coupled to a transmon qubit, Marta Pita-Vidal, Arno Bargerbos, Rok Žitko, Lukas J Splitthoff, Lukas Grünhaupt, Jaap J Wesdorp, Yu Liu, Leo P Kouwenhoven, Ramón Aguado, Bernard van Heck, Angela Kou, Christian Kraglund Andersen, Nature Physics, 19, 1110 (2023)
[5] Optimal Majoranas in Mesoscopic Kitaev Chains, M Alvarado, R Seoane Souto, María José Calderón, Ramón Aguado, arXiv preprint arXiv:2604.13945.
[6] Single-shot parity readout of a minimal Kitaev chain, Nick van Loo, Francesco Zatelli, Gorm O Steffensen, Bart Roovers, Guanzhong Wang, Thomas Van Caekenberghe, Alberto Bordin, David van Driel, Yining Zhang, Wietze D Huisman, Ghada Badawy, Erik PAM Bakkers, Grzegorz P Mazur, Ramón Aguado, Leo P Kouwenhoven, Nature 650, 334-339 (2026)