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Explaining Grover's algorithm with a colony of ants: a pedagogical model for making quantum technology comprehensible

Schalkers, M.A. (author), Dankers, K.T. (author), Wimmer, M.T. (author), Vermaas, P.E. (author)

The rapid growth of quantum technologies requires an increasing number of physicists, computer scientists, and engineers who can work on these technologies. For educating these professionals, quantum mechanics should stop being perceived as incomprehensible. In this paper we contribute to this change by presenting a pedagogical model for...

journal article 2024

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Fusion protocol for Majorana modes in coupled quantum dots

Liu, Chun Xiao (author), Pan, Haining (author), Setiawan, F. (author), Wimmer, M.T. (author), Sau, Jay D. (author)

In a recent breakthrough experiment [Nature (London) 614, 445 (2023)10.1038/s41586-022-05585-1], signatures of Majorana zero modes have been observed in tunnel spectroscopy for a minimal Kitaev chain constructed from coupled quantum dots. However, as Ising anyons, Majoranas' most fundamental property of non-Abelian statistics is yet to be...

journal article 2023

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Tunable Crossed Andreev Reflection and Elastic Cotunneling in Hybrid Nanowires

Bordin, A. (author), Wang, Guanzhong (author), Liu, Chun Xiao (author), ten Haaf, S.L.D. (author), van Loo, N. (author), Mazur, G.P. (author), Xu, D. (author), van Driel, D. (author), Zatelli, F. (author), Gazibegovic, Sasa (author), Badawy, Ghada (author), Bakkers, Erik P.A.M. (author), Wimmer, M.T. (author), Kouwenhoven, Leo P. (author), Dvir, T. (author)

A short superconducting segment can couple attached quantum dots via elastic cotunneling (ECT) and crossed Andreev reflection (CAR). Such coupled quantum dots can host Majorana bound states provided that the ratio between CAR and ECT can be controlled. Metallic superconductors have so far been shown to mediate such tunneling phenomena, albeit...

journal article 2023

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Realization of a minimal Kitaev chain in coupled quantum dots

Dvir, T. (author), Wang, Guanzhong (author), van Loo, N. (author), Liu, C. (author), Mazur, G.P. (author), Bordin, A. (author), ten Haaf, S.L.D. (author), van Driel, D. (author), Zatelli, F. (author), Li, X. (author), Malinowski, F.K. (author), Gazibegovic, Sasa (author), Badawy, G.H.A. (author), Bakkers, Erik P.A.M. (author), Wimmer, M.T. (author), Kouwenhoven, Leo P. (author)

Majorana bound states constitute one of the simplest examples of emergent non-Abelian excitations in condensed matter physics. A toy model proposed by Kitaev shows that such states can arise at the ends of a spinless p-wave superconducting chain¹. Practical proposals for its realization^2,3 require coupling neighbouring...

journal article 2023

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Optimizing the topological properties of semiconductor-ferromagnet-superconductor heterostructures

Liu, Chun Xiao (author), Wimmer, M.T. (author)

We study the electronic properties of a planar semiconductor-superconductor heterostructure, in which a thin ferromagnetic insulator layer lies in between and acts as a spin filtering barrier. We find that in such a system one can simultaneously enhance the strengths of all the three important induced physical quantities, i.e., Rashba spin...

journal article 2022

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Singlet and triplet Cooper pair splitting in hybrid superconducting nanowires

Wang, Guanzhong (author), Dvir, T. (author), Mazur, G.P. (author), Liu, C. (author), van Loo, N. (author), ten Haaf, S.L.D. (author), Bordin, A. (author), Gazibegovic, Sasa (author), Badawy, G.H.A. (author), Bakkers, Erik P.A.M. (author), Wimmer, M.T. (author), Kouwenhoven, Leo P. (author)

In most naturally occurring superconductors, electrons with opposite spins form Cooper pairs. This includes both conventional s-wave superconductors such as aluminium, as well as high-transition-temperature, d-wave superconductors. Materials with intrinsic p-wave superconductivity, hosting Cooper pairs made of equal-spin electrons, have not...

journal article 2022

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Tunable Superconducting Coupling of Quantum Dots via Andreev Bound States in Semiconductor-Superconductor Nanowires

Liu, C. (author), Wang, Guanzhong (author), Dvir, T. (author), Wimmer, M.T. (author)

Semiconductor quantum dots have proven to be a useful platform for quantum simulation in the solid state. However, implementing a superconducting coupling between quantum dots mediated by a Cooper pair has so far suffered from limited tunability and strong suppression. This has limited applications such as Cooper pair splitting and quantum...

journal article 2022

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Josephson current via an isolated Majorana zero mode

Liu, C. (author), van Heck, B. (author), Wimmer, M.T. (author)

We study the equilibrium dc Josephson current in a junction between an s-wave and a topological superconductor. Cooper pairs from the s-wave superconducting lead can transfer to the topological side either via an unpaired Majorana zero mode localized near the junction or via the above-gap continuum states. We find that the Majorana...

journal article 2021

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Minimal Zeeman field requirement for a topological transition in superconductors

Pöyhönen, K.K. (author), Varjas, D. (author), Wimmer, M.T. (author), Akhmerov, A.R. (author)

Platforms for creating Majorana quasiparticles rely on superconductivity and breaking of time-reversal symmetry. By studying continuous deformations to known trivial states, we find that the relationship between superconducting pairing and time reversal breaking imposes rigorous bounds on the topology of the system. Applying these bounds to s...

journal article 2021

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Quantized and unquantized zero-bias tunneling conductance peaks in Majorana nanowires: Conductance below and above 2e2/h

Pan, Haining (author), Liu, Chun Xiao (author), Wimmer, M.T. (author), Das Sarma, Sankar (author)

Majorana zero modes can appear at the wire ends of a one-dimensional topological superconductor and manifest themselves as a quantized zero-bias conductance peak in the tunneling spectroscopy of normal-superconductor junctions. However, in superconductor-semiconductor hybrid nanowires, zero-bias conductance peaks may arise owing to...

journal article 2021

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Electronic properties of InAs/EuS/Al hybrid nanowires

Liu, C. (author), Schuwalow, Sergej (author), Liu, Yu (author), Vilkelis, K. (author), Manesco, A. L.R. (author), Krogstrup, P. (author), Wimmer, M.T. (author)

We study the electronic properties of InAs/EuS/Al heterostructures as explored in a recent experiment, combining both spectroscopic results and microscopic device simulations. In particular, we use angle-resolved photoemission spectroscopy to investigate the band bending at the InAs/EuS interface. The resulting band offset value serves as an...

journal article 2021

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Conductance asymmetries in mesoscopic superconducting devices due to finite bias

De Almeida Nascimento e Melo, A.A. (author), Liu, C. (author), Rozek, P.M. (author), Rosdahl, T.O. (author), Wimmer, M.T. (author)

Tunneling conductance spectroscopy in normal metal-superconductor junctions is an important tool for probing Andreev bound states in mesoscopic superconducting devices, such as Majorana nanowires. In an ideal superconducting device, the subgap conductance obeys specific symmetry relations, due to particle-hole symmetry and unitarity of the...

journal article 2021

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Enhanced Proximity Effect in Zigzag-Shaped Majorana Josephson Junctions

Laeven, T.M. (author), Nijholt, B. (author), Wimmer, M.T. (author), Akhmerov, A.R. (author)

High density superconductor-semiconductor-superconductor junctions have a small induced superconducting gap due to the quasiparticle trajectories with a large momentum parallel to the junction having a very long flight time. Because a large induced gap protects Majorana modes, these long trajectories constrain Majorana devices to a low...

journal article 2020

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Reproducing topological properties with quasi-Majorana states

Vuik, A. (author), Nijholt, B. (author), Akhmerov, A.R. (author), Wimmer, M.T. (author)

Andreev bound states in hybrid superconductor-semiconductor devices can have near-zero energy in the topologically trivial regime as long as the confinement potential is sufficiently smooth. These quasi-Majorana states show zero-bias conductance features in a topologically trivial phase, mimicking spatially separated topological Majorana...

journal article 2019

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Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires

Bommer, J.D.S. (author), Zhang, Hao (author), Gül, Önder (author), Nijholt, B. (author), Wimmer, M.T. (author), Rybakov, Filipp N. (author), Garaud, Julien (author), Car, Diana (author), Plissard, Sébastien R. (author), Bakkers, E.P.A.M. (author), Kouwenhoven, Leo P. (author)

Spin-orbit interaction (SOI) plays a key role in creating Majorana zero modes in semiconductor nanowires proximity coupled to a superconductor. We track the evolution of the induced superconducting gap in InSb nanowires coupled to a NbTiN superconductor in a large range of magnetic field strengths and orientations. Based on realistic...

journal article 2019

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Unified numerical approach to topological semiconductor-superconductor heterostructures

Winkler, Georg W. (author), Antipov, Andrey E. (author), van Heck, B. (author), Soluyanov, Alexey A. (author), Glazman, Leonid I. (author), Wimmer, M.T. (author), Lutchyn, Roman M. (author)

We develop a unified numerical approach for modeling semiconductor-superconductor heterostructures. All the key physical ingredients of these systems - orbital effect of magnetic field, superconducting proximity effect, and electrostatic environment - are taken into account on equal footing in a realistic device geometry. As a model system,...

journal article 2019

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Supercurrent carried by nonequilibrium quasiparticles in a multiterminal Josephson junction

Nowak, M. P. (author), Wimmer, M.T. (author), Akhmerov, A.R. (author)

We theoretically study coherent multiple Andreev reflections in a biased three-terminal Josephson junction. We demonstrate that the direct current flowing through the junction consists of supercurrent components when the bias voltages are commensurate. This dissipationless current depends on the phase in the superconducting leads and stems...

journal article 2019

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A general algorithm for computing bound states in infinite tight-binding systems

Istas, Mathieu (author), Groth, Christoph (author), Akhmerov, A.R. (author), Wimmer, M.T. (author), Waintal, Xavier (author)

We propose a robust and efficient algorithm for computing bound states of infinite tight-binding systems that are made up of a finite scattering region connected to semi-infinite leads. Our method uses wave matching in close analogy to the approaches used to obtain propagating states and scattering matrices. We show that our algorithm is robust...

journal article 2018

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H /e Superconducting Quantum Interference through Trivial Edge States in InAs

de Vries, F.K. (author), Timmerman, Tom (author), Ostroukh, Viacheslav P. (author), van Veen, J. (author), Beukman, A.J.A. (author), Qu, F. (author), Wimmer, M.T. (author), Kiselev, Andrey A. (author), Kouwenhoven, Leo P. (author)

Josephson junctions defined in strong spin orbit semiconductors are highly interesting for the search for topological systems. However, next to topological edge states that emerge in a sufficient magnetic field, trivial edge states can also occur. We study the trivial edge states with superconducting quantum interference measurements on...

journal article 2018

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Robust helical edge transport in quantum spin Hall quantum wells

Skolasinski, R.J. (author), Pikulin, D. (author), Alicea, Jason (author), Wimmer, M.T. (author)

We show that edge-state transport in semiconductor-based quantum spin Hall systems is unexpectedly robust to magnetic fields. The origin for this robustness lies in an intrinsic suppression of the edge-state g-factor and the fact that the edge-state Dirac point is typically hidden in the valence band. A detailed k·p band-structure analysis...

journal article 2018