NONLOCAL: ERC Synergy Grant

NONLOCAL: ERC Synergy Grant is a Horizon 2020 grant awarded to the Principle Investigators Professors Karsten Flensberg, Ferdinand Kuemmeth, Charles M. Marcus, and Martin Leijnse. Flensberg and Kuemmeth are based at the Center for Quantum Devices at the Niels Bohr Institute, while Leijnse is based at NanoLund: Center for Nanoscience, Lund University, and Marcus at University of Washington, Seattle, US.

The NONLOCAL project kicked off on 1 November 2020 and will run until 30 April 2027. The program involves design and implementation of systems with multiple Majorana bound states (MBSs) and quantum dots, thus taking advantage of well-known quantum systems for diagnostics of the topological properties of MBSs, including spinful quantum dots, charge sensing and quantum capacitance measurements. It takes it’s beginning in a number of experiments that reveal the inner nature of the MBSs, in particular their spin texture, spatial extend, and most importantly the lifetime of pairs of MBSs candidates both with finite and negligible overlap.

What is known at this time is that zero bias peaks consistent with Majorana interpretations are more or less routinely observed and have been reported in a number of papers. Moreover, superconductor islands made from the proximitized nanowires consistently show a transition from only accepting electron pairs – as expected for a trivial superconductor – to a regime where the even and odd occupied states of a superconducting island are degenerated. The latter is consistent with a transition to a topologically non-trivial state. In addition, there are many details in the transport spectroscopy that support the MBS interpretation. On the theory side, the agreement with experiments is based on effective models that include the main ingredients, spin-orbit coupling and induced pairing. However, the exact microscopic nature of both ingredients is to a large extend still not understood. In this project, we introduce a joint experimental and theoretical research program with the objective of investigating the physics of nonlocal and nonabelian particles using MBSs.

The already published papers include, among other key points, theory on measurement setup for the important parity-to-charge conversion plus protocols for investigation of the nonabelian and nonlocal properties. Preprint papers include experimental papers on the same topic as well as novel superconductor-semiconductor hybrid systems. 

The project aims to bring new insight into a new class of macroscopic quantum phenomena of topological origin. It is also possible that results will lead to applications in the form of quantum computation or quantum information storage.

Publications (updated July 2024)

    1. M.T. Deng, Carlos Payá, Pablo San-Jose, Elsa Prada, C. M. Marcus, S. Vaitiekėnas. Caroli–de Gennes–Matricon Analogs in Full-Shell Hybrid Nanowires. Phys. Rev. Lett. 134, 206302 – (Published 22 May, 2025).

    2. Samuel D. Escribano, Anders Enevold Dahl, Karsten Flensberg, Yuval Oreg. Phase-controlled minimal Kitaev chain in multiterminal Josephson junctions. Phys. Rev. B 111, 195433 – (Published 30 May, 2025).

    3. L. Banszerus, C. W. Andersson, W. Marshall, T. Lindemann, M. J. Manfra, C. M. Marcus, S. Vaitiekėnas. Hybrid Josephson Rhombus: A Superconducting Element with Tailored Current-Phase Relation. Phys. Rev. X 15, 011021 – (Published 4 February, 2025).

    4. Rubén Seoane Souto, Virgil V. Baran, Maximilian Nitsch, Lorenzo Maffi, Jens Paaske, Martin Leijnse, Michele Burrello. Majorana modes in quantum dots coupled via a floating superconducting island. Phys. Rev. B 111, 174501 – (Published 1 May, 2025).

    5. Lazar Lakic, William I. L. Lawrie, David van Driel, Lucas E. A. Stehouwer, Yao Su, Menno Veldhorst, Giordano Scappucci, Ferdinand Kuemmeth, Anasua Chatterjee. A quantum dot in germanium proximitized by a superconductor. Nature Materials 24, 552 (2025).

    6. Marco Valentini, Rubén Seoane Souto, Maksim Borovkov, Peter Krogstrup, Yigal Meir, Martin Leijnse, Jeroen Danon, Georgios Katsaros. Subgap transport in superconductor-semiconductor hybrid islands: Weak and strong coupling regimes. Phys. Rev. Research 7, 023022 – (Published 8 April, 2025).

    7. L. Banszerus, W. Marshall, C. W. Andersson, T. Lindemann, M. J. Manfra, C. M. Marcus, S. Vaitiekėnas. Voltage-Controlled Synthesis of Higher Harmonics in Hybrid Josephson Junction Circuits. hys. Rev. Lett. 133, 186303 – (Published 31 October, 2024).

    8. D. Razmadze, R. Seoane Souto, E. C. T. O'Farrell, P. Krogstrup, M. Leijnse, C. M. Marcus, S. Vaitiekėnas. Supercurrent transport through . Phys. Rev. B 109, L041302 – (Published 19 January, 2024).

    9. Anna Sandberg, Oladunjoye A. Awoga, Annica M. Black-Schaffer, Patric Holmvall. Josephson effect in a Fibonacci quasicrystal. Phys. Rev. B 110, 104513 – Published 18 September, 2024).

    10. Athanasios Tsintzis, Rubén Seoane Souto, Karsten Flensberg, Jeroen Danon, Martin Leijnse. Majorana Qubits and Non-Abelian Physics in Quantum Dot–Based Minimal Kitaev Chains. PRX Quantum 5, 010323 – (Published 8 February, 2024).

    11. Oladunjoye A. Awoga, Jorge Cayao. Identifying trivial and Majorana zero-energy modes using the Majorana polarization. Phys. Rev. B 110, 165404 – (Published 2 October, 2024).

    12. Svend Krøjer, Anders Enevold Dahl, Kasper Sangild Christensen, Morten Kjaergaard, Karsten Flensberg. Fast universal control of a flux qubit via exponentially tunable wave-function overlap. Phys. Rev. Research 6, 023064 – (Published 18 April, 2024).

    13. Max Geier, Rubén Seoane Souto, Jens Schulenborg, Serwan Asaad, Martin Leijnse, Karsten Flensberg. Fermion-parity qubit in a proximitized double quantum dot. Phys. Rev. Research 6, 023281 – (Published 17 June, 2024).

    14. Oladunjoye A. Awoga, Ioannis Ioannidis, Archana Mishra, Martin Leijnse, Mircea Trif, Thore Posske. Controlling Majorana hybridization in magnetic chain-superconductor systems. Phys. Rev. Research 6, 033154 – (Published 9 August, 2024).

    15. Rousan Debbarma, Athanasios Tsintzis, Markus Aspegren, Rubén Seoane Souto, Sebastian Lehmann, Kimberly Dick, Martin Leijnse, Claes Thelander. Josephson Junction. Phys. Rev. Lett. 131, 256001 – (Published 21 December, 2023).

    16. Maximilian Nitsch, Rubén Seoane Souto, Stephanie Matern, Martin Leijnse. Transport-based fusion that distinguishes between Majorana and Andreev bound states. Phys. Rev. B 109, 165404 – (Published 1 April, 2024).

    17. Aksel Kobiałka, Oladunjoye A. Awoga, Martin Leijnse, Tadeusz Domański, Patric Holmvall, Annica M. Black-Schaffer. Topological superconductivity in Fibonacci quasicrystals. Phys. Rev. B 110, 134508 – (Published 9 October, 2024).

    18. Rubén Seoane Souto, Martin Leijnse, Constantin Schrade, Marco Valentini, Georgios Katsaros, Jeroen Danon. Tuning the Josephson diode response with an ac current. Phys. Rev. Research 6, L022002 (Published 3 April, 2024).

    19. Viktor Svensson, Martin Leijnse (Dec. 2024). Quantum dot based Kitaev chains: Majorana quality measures and scaling with increasing chain length. Phys. Rev. B 110, 155436 – (Published 25 October, 2024).

    20. A. Maiani, R. Seoane Souto, M. Leijnse, and K. Flensberg. (2021). Topological superconductivity in semiconductor–superconductor–magnetic-insulator heterostructures. Phys. Rev. B. 103, 104508 (Published 12 March 2021)

    21. M. Geier, I. Cosma Fulga, and A. Lau. (2021). Bulk-boundary-defect correspondence at disclinations in rotation-symmetric topological insulators and superconductors. SciPost Phys. 10, 092 (Published 26 April 2021)

    22. J. Schulenborg, M. Burello, M. Leijnse, and K. Flensberg. (2021). Multilevel effects in quantum dot based parity-to-charge conversion of Majorana box qubits. Phys. Rev. B. 103, 245407 (Published 3 June 2021)

    23. D. Kuzmanovski, R. Seoane Souto, and A. V. Balatsky. (2021). Persistent current noice in narrow Josephson junctions. Phys. Rev. B. 104, L100505 (Published 21 September 2021)

    24. R. Seoane Souto, A. E. Feiguin, A. Martín-Rodero, and A. Levy Yeyati. (2021). Transient dynamics of a magnetic impurity coupled to superconducting electrodes: Exact numerics versus perturbation theory. Phys. Rev. B. 104, 214506 (Published 16 December 2021)

    25. S. Krøjer, R. Seoane Souto, and K. Flensberg. (2022). Demonstrating Majorana non-Abelianproperties using fast adiabatic charge transfer. Phys. Rev. B. 105, 045425 (Published 28 January 2022)

    26. S. Vaitiekènas, R. Seoane Souto, Y. Liu, P. Krogstrup, K. Flensberg, M. Leijnse, and C. M. Marcus. (2022). Evidence for spin-polarized bound states in semiconductor-superconductor-ferromagnetic-insulator islands. Phys. Rev. B. 105, L041304 (Published 31 January 2022)

    27. R. Seoane Souto, M. Leijnse. (2022). Fusion rules in a Majorana single-charge transistor, SciPost Phys. 12, 161 (Published 16 May 2022)

    28. A.Tsintzis, R.Seoane Souto, and M. Leijnse. (2022). Creating and detecting poor man's Majorana bound states in interacting quantum dots. Phys. Rev. B 106, L201404 (Published 17 November 2022)

    29. T. Li, M. Geier, J. Inghamand, and H. D Scammell. (2022). Higher-order topological superconductivity from repulsive interactions in kagome and honeycomb systems. 2D Mater. 9, 015031 (Published 21 December 2021)

    30. M. Nitsch, R. Seoane Souto, and M. Leijnse. (2022). Interference and parity blockade in transport through a Majorana box. Phys. Rev. B 106, L201305 (Published 17 November 2022).

    31. S. D. Escribano, A. Maiani, M. Leijnse, K. Flensberg, Y. Oreg, A. L. Yeyati, E. Prada, and R. Seoane Souto. (2022). Semiconductor-ferromagnet-superconductor planar heterostructures for 1D topological superconductivity. npj Quantum Materials volume 7, Article number: 81 (Published 18 August 2022)

    32. S. Simon, M. Geier, and P. W. Brouwer. (2022). Higher-order topological semimetals and nodal superconductors with an order-two crystalline symmetry. Phys. Rev. B 106, 035105 (Published 5 July 2022)

    33. I. E. Nielsen, K. Flensberg, R. Egger, and M. Burrello. (2022). Readout of Parafermionic States by Transport Measurements. Phys. Rev. Lett. 129, 037703 – Published 13 July 2022

    34. H. D. Scammell, J. Ingham, M. Geier, and T. Li. (2022). Intrinsic first- and higher-order topological superconductivity in a doped topological insulator. Phys. Rev. B 105, 195149 (Published 31 May 2022)

    35. B. Sbierski, M. Geier, A.-P. Li, M. Brahlek, R. G. Moore, and J. E. Moore. (2022). Identifying Majorana vortex modes via nonlocal transport. Phys. Rev. B 106, 035413 (Published 14 July 2022)

    36. O. Krause, B. Brovang, T. Rasmussen,  A. Chatterjee, and F. Kuemmeth. Estimation of Convex Polytopes for Automatic Discovery of Charge State Transitions in Quantum Dot Arrays. Electronics. (2022) 11(15), 2327 (Published 27 July 2022)

    37. A. Chatterjee, F. Ansaloni, T. Rasmussen, B. Brovang, F. Fedele, H. Bohuslavskyi, O. Krause, and F. Kuemmeth. (2022). Autonomous Estimation of High-Dimensional Coulomb Diamonds from Sparse Measurements. Phys. Rev. Applied 18, 064040 (Published 14 December 2022)

    38. R. S. Souto, M. M. Wauters, K. Flensberg, M. Leijnse, and M. Burrello. (2022). Multiterminal transport spectroscopy of subgap states in Coulomb-blockaded superconductors. Phys. Rev. B. 106, 235425 (Published 22 December 2022)

    39. R. S. Souto, M. Leijnse, and C. Schrade. Josephson Diode Effect in Supercurrent Interferometers. (2022). Phys. Rev. Lett. 129, 267702 (Published 22 December 2022)

    40. D. Razmadze, R. Seoane Souto, L. Galletti, A. Maiani, Y. Liu, P. Krogstrup, C. Schrade, A. Gyenis, C. M. Marcus, and S. Vaitiekėnas. (2023). Supercurrent reversal in ferromagnetic hybrid nanowire Josephson junctions. Phys. Rev. B. 107, L081301 (Published 13 February 2023)

    41. F. Vigneau, F. Fedele, A. Chatterjee, D. Reilly, F. Kuemmeth, M. Fernando Gonzalez-Zalba, E. Laird, and N. Ares. (2023) Probing quantum devices with radio-frequency reflectometry. Appl. Phys. Rev. 10, 021305 (Published 24 February 2023)
    42. A. Maiani, K. Flensberg, M. Leijnse, C. Schrade, S. Vaitiekėnas, and R. S. Souto. (2023). Nonsinusoidal current-phase relations in semiconductor–superconductor– ferromagnetic insulator devices. Phys. Rev. B. 107, 245415 (Published 13 June 2023)

    43. A. Banerjee, M. Geier, M. A. Rahman, C. Thomas; T. Wang, M. J. Manfra, K. Flensberg, and C. M. Marcus. Phase Asymmetry of Andreev Spectra from Cooper-Pair Momentum. Phys Rev. Lett. 131, 196301 (Published 9 November 2023)
    44. R. S. Souto, A. Tsintzis, M. Leijnse, and J. Danon. (2023). Probing Majorana localization in minimal Kitaev chains through a quantum dot. Phys. Rev. Research. 5, 043182. (Published 27 November 2023)

    45. N. C. Jayarama, and V. Svensson. Real-space circuit complexity as a probe of phase diagrams. (2023). Phys. Rev. B. 207, 075122 (Published 9 February 2023)

    46. O. A. Awoga, M. Leijnse, A. M. Black-Schaffer, and J. Cayao. Mitigating disorder-induced zero-energy states in weakly coupled superconductor-semiconductor hybrid systems. (2023). Phys Rev. B. 107, 184519 (Published 30 May 2023)

    47. A-G. Penner, K. Flensberg, L. I. Glazman, and F. von Oppen. Resistivity Tensor of Vortex-Lattice States in Josephson Junction Arrays. (2023) Phys. Rev. Letters. 131, 206001 (Published 14 November 2023)

    48. A. Banerjee, M. Geier, M. A Rahman, D. S. Sanchez, C. Thomas, T. Wang, M. J. Manfra, K. Flensberg, and C. M. Marcus. Control of Andreev Bound States Using Superconducting Phase Texture. (2023). Phys. Rev. Lett. 130, 116203 (Published  15 March 2023)

    49. J. Schulenborg, S. Krøjer, M. Burrello, M. Leijnse, and K. Flensberg. Detecting Majorana modes by readout of poisoning-induced parity flips. (2023) Phys. Rev. B. 107, L121401 (Published 3 March 2023)

    50. W. Samuelson, V. Svensson, and M. Leijnse. Minimal quantum dot-based Kitaev chain with only local superconducting proximity effect. (2024). Phys Rev. B. 109. 035415 (Published 12 January 2024)