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Mitigation of Quasiparticle Loss in Superconducting Qubits by Phonon Scattering

Bargerbos, A. (author), Splitthoff, L.J. (author), Pita-Vidal, Marta (author), Wesdorp, J.J. (author), Liu, Yu (author), Krogstrup, Peter (author), Kouwenhoven, Leo P. (author), Andersen, C.K. (author), Grünhaupt, L. (author)

Quantum error correction will be an essential ingredient in realizing fault-tolerant quantum computing. However, most correction schemes rely on the assumption that errors are sufficiently uncorrelated in space and time. In superconducting qubits, this assumption is drastically violated in the presence of ionizing radiation, which creates bursts...

journal article 2023

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Lower-temperature fabrication of airbridges by grayscale lithography to increase yield of nanowire transmons in circuit QED quantum processors

Stavenga, T. (author), Khan, S. A. (author), Liu, Y. (author), Krogstrup, P. (author), DiCarlo, L. (author)

Quantum hardware based on circuit quantum electrodynamics makes extensive use of airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Airbridges also provide an interconnect enabling transmission lines to cross. Traditional airbridge fabrication produces a curved profile by reflowing resist at...

journal article 2023

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Gate-tunable superconductivity in hybrid InSb-Pb nanowires

Chen, Yan (author), van Driel, D. (author), Lampadaris, Charalampos (author), Khan, Sabbir A. (author), Alattallah, Khalifah (author), Zeng, Lunjie (author), Olsson, Eva (author), Dvir, T. (author), Krogstrup, Peter (author), Liu, Yu (author)

We present a report on hybrid InSb-Pb nanowires that combine high spin-orbit coupling with a high critical field and a large superconducting gap. Material characterization indicates the Pb layer of high crystal quality on the nanowire side facets. Hard induced superconducting gaps and gate-tunable supercurrent are observed in the hybrid...

journal article 2023

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Dynamical Polarization of the Fermion Parity in a Nanowire Josephson Junction

Wesdorp, J.J. (author), Grünhaupt, L. (author), Vaartjes, A. (author), Pita-Vidal, Marta (author), Bargerbos, A. (author), Splitthoff, L.J. (author), Krogstrup, P. (author), van Heck, B. (author), de Lange, G. (author)

Josephson junctions in InAs nanowires proximitized with an Al shell can host gate-tunable Andreev bound states. Depending on the bound state occupation, the fermion parity of the junction can be even or odd. Coherent control of Andreev bound states has recently been achieved within each parity sector, but it is impeded by incoherent parity...

journal article 2023

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Microwave Susceptibility Observation of Interacting Many-Body Andreev States

Fatemi, V. (author), Kurilovich, P. D. (author), Hays, M. (author), Bouman, D. (author), Connolly, T. (author), Diamond, S. (author), Krogstrup, P. (author), Geresdi, A. (author), Devoret, M. H. (author)

Electrostatic charging affects the many-body spectrum of Andreev states, yet its influence on their microwave properties has not been elucidated. We developed a circuit quantum electrodynamics probe that, in addition to transition spectroscopy, measures the microwave susceptibility of different states of a semiconductor nanowire weak link...

journal article 2022

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Radio-Frequency C - V Measurements with Subattofarad Sensitivity

Malinowski, F.K. (author), Han, L. (author), de Jong, D. (author), Wang, Ji Yin (author), Prosko, C.G. (author), Krogstrup, Peter (author), Bakkers, Erik P.A.M. (author), Kouwenhoven, Leo P. (author), Koski, Jonne V. (author)

We demonstrate the use of radio-frequency (rf) resonators to measure the capacitance of nanoscale semiconducting devices in field-effect transistor configurations. The rf resonator is attached to the gate or the lead of the device. Consequently, tuning the carrier density in the conducting channel of the device affects the resonance frequency...

journal article 2022

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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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Magnetic-field-compatible superconducting transmon qubit

Kringhøj, A. (author), Larsen, T. W. (author), Erlandsson, O. (author), Uilhoorn, W. (author), Kroll, J. (author), Hesselberg, M. (author), McNeil, R. P.G. (author), Krogstrup, P. (author), Casparis, L. (author), Marcus, C. M. (author)

We present a hybrid semiconductor-based superconducting qubit device that remains coherent at magnetic fields up to 1 T. The qubit transition frequency exhibits periodic oscillations with the magnetic field, consistent with interference effects due to the magnetic flux threading the cross section of the proximitized semiconductor nanowire...

journal article 2021

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Andreev Modes from Phase Winding in a Full-Shell Nanowire-Based Transmon

Kringhøj, A. (author), Winkler, G. W. (author), Larsen, T. W. (author), Sabonis, D. (author), Erlandsson, O. (author), Krogstrup, P. (author), van Heck, B. (author), Petersson, K. D. (author), Marcus, C. M. (author)

We investigate transmon qubits made from semiconductor nanowires with a fully surrounding superconducting shell. In the regime of reentrant superconductivity associated with the destructive Little-Parks effect, numerous coherent transitions are observed in the first reentrant lobe, where the shell carries 2π winding of superconducting phase,...

journal article 2021

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Rapid Microwave-Only Characterization and Readout of Quantum Dots Using Multiplexed Gigahertz-Frequency Resonators

de Jong, D. (author), Prosko, C.G. (author), Waardenburg, D.M.A. (author), Han, L. (author), Malinowski, F.K. (author), Krogstrup, P. (author), Kouwenhoven, Leo P. (author), Koski, J.V. (author), Pfaff, W. (author)

Superconducting resonators enable fast characterization and readout of mesoscopic quantum devices. Finding ways to perform measurements of interest on such devices using resonators only is therefore of great practical relevance. We report an experimental investigation of an InAs nanowire multiquantum dot device by probing gigahertz resonators...

journal article 2021

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Triplet-blockaded Josephson supercurrent in double quantum dots

Bouman, D. (author), van Gulik, R.J.J. (author), Steffensen, Gorm (author), Pataki, Dávid (author), Boross, Péter (author), Krogstrup, Peter (author), Nygård, Jesper (author), Paaske, Jens (author), Pályi, András (author), Geresdi, A. (author)

Serial double quantum dots created in semiconductor nanostructures provide a versatile platform for investigating two-electron spin quantum states, which can be tuned by electrostatic gating and an external magnetic field. In this Rapid Communication, we directly measure the supercurrent reversal between adjacent charge states of an InAs...

journal article 2020

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Suppressed Charge Dispersion via Resonant Tunneling in a Single-Channel Transmon

Kringhøj, A. (author), van Heck, B. (author), Larsen, T. W. (author), Erlandsson, O. (author), Sabonis, D. (author), Krogstrup, P. (author), Casparis, L. (author), Petersson, K. D. (author), Marcus, C. M. (author)

We demonstrate strong suppression of charge dispersion in a semiconductor-based transmon qubit across Josephson resonances associated with a quantum dot in the junction. On resonance, dispersion is drastically reduced compared to conventional transmons with corresponding Josephson and charging energies. We develop a model of qubit dispersion...

journal article 2020

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Observation of Vanishing Charge Dispersion of a Nearly Open Superconducting Island

Bargerbos, A. (author), Uilhoorn, W. (author), Yang, C. (author), Krogstrup, Peter (author), Kouwenhoven, Leo P. (author), de Lange, G. (author), van Heck, B. (author), Kou, A. (author)

Isolation from the environment determines the extent to which charge is confined on an island, which manifests as Coulomb oscillations, such as charge dispersion. We investigate the charge dispersion of a nanowire transmon hosting a quantum dot in the junction. We observe rapid suppression of the charge dispersion with increasing junction...

journal article 2020

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Destructive Little-Parks Effect in a Full-Shell Nanowire-Based Transmon

Sabonis, Deividas (author), Erlandsson, Oscar (author), Kringhøj, Anders (author), van Heck, B. (author), Larsen, Thorvald W. (author), Petkovic, I. (author), Krogstrup, P. (author), Petersson, Karl D. (author), Marcus, Charles M. (author)

A semiconductor transmon with an epitaxial Al shell fully surrounding an InAs nanowire core is investigated in the low EJ/EC regime. Little-Parks oscillations as a function of flux along the hybrid wire axis are destructive, creating lobes of reentrant superconductivity separated by a metallic state at a half quantum of applied flux. In the...

journal article 2020

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Gate-Tunable Field-Compatible Fluxonium

Pita-Vidal, Marta (author), Bargerbos, A. (author), Yang, C. (author), van Woerkom, D.J. (author), Pfaff, W. (author), Haider, S.N. (author), Krogstrup, Peter (author), Kouwenhoven, Leo P. (author), de Lange, G. (author), Kou, A. (author)

Hybrid superconducting circuits, which integrate nonsuperconducting elements into a circuit quantum electrodynamics (cQED) architecture, expand the possible applications of cQED. Building hybrid circuits that work in large magnetic fields presents even further possibilities, such as the probing of spin-polarized Andreev bound states and the...

journal article 2020

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Revealing charge-tunneling processes between a quantum dot and a superconducting island through gate sensing

van Veen, J. (author), de Jong, D. (author), Han, L. (author), Prosko, C.G. (author), Krogstrup, P. (author), Watson, J.D. (author), Kouwenhoven, Leo P. (author), Pfaff, W. (author)

We report direct detection of charge tunneling between a quantum dot and a superconducting island through radio-frequency gate sensing. We are able to resolve spin-dependent quasiparticle tunneling as well as two-particle tunneling involving Cooper pairs. The quantum dot can act as an RF-only sensor to characterize the superconductor addition...

journal article 2019

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Rapid Detection of Coherent Tunneling in an InAs Nanowire Quantum Dot through Dispersive Gate Sensing

de Jong, D. (author), van Veen, J. (author), Binci, L. (author), Singh, A. (author), Krogstrup, P. (author), Kouwenhoven, Leo P. (author), Pfaff, W. (author), Watson, J.D. (author)

Dispersive sensing is a powerful technique that enables scalable and high-fidelity readout of solid-state quantum bits. In particular, gate-based dispersive sensing has been proposed as the readout mechanism for future topological qubits, which can be measured by single electrons tunneling through zero-energy modes. The development of such a...

journal article 2019

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Broadband microwave spectroscopy of semiconductor nanowire-based Cooper-pair transistors

Proutski, A. (author), Laroche, D. (author), Van 'T Hooft, Bas (author), Krogstrup, Peter (author), Nygård, Jesper (author), Kouwenhoven, Leo P. (author), Geresdi, A. (author)

The Cooper-pair transistor (CPT), a small superconducting island enclosed between two Josephson weak links, is the atomic building block of various superconducting quantum circuits. Utilizing gate-tunable semiconductor channels as weak links, the energy scale associated with the Josephson tunneling can be changed with respect to the charging...

journal article 2019

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Selective-area chemical beam epitaxy of in-plane InAs one-dimensional channels grown on InP(001), InP(111)B, and InP(011) surfaces

Lee, Joon Sue (author), Koelling, Sebastian (author), Verheijen, Marcel A. (author), Petkovic, Ivana (author), Schaller, V. (author), Marcus, Charles M. (author), Krogstrup, Peter (author), Kouwenhoven, Leo P. (author), Bakkers, E.P.A.M. (author)

We report on the selective-area chemical beam epitaxial growth of InAs in-plane, one-dimensional (1D) channels using patterned SiO2-coated InP(001), InP(111)B, and InP(011) substrates to establish a scalable platform for topological superconductor networks. Top-view scanning electron micrographs show excellent surface selectivity and...

journal article 2019

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Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

Lüthi, F. (author), Stavenga, T. (author), Enzing, O.W. (author), Bruno, A. (author), Dickel, C. (author), Langford, N.K. (author), Rol, M.A. (author), Jespersen, T. S. (author), Nygård, J. (author), Krogstrup, P. (author), DiCarlo, L. (author)

We present an experimental study of flux- and gate-tunable nanowire transmons with state-of-the-art relaxation time allowing quantitative extraction of flux and charge noise coupling to the Josephson energy. We evidence coherence sweet spots for charge, tuned by voltage on a proximal side gate, where first order sensitivity to switching two...

journal article 2018