Gate-Tunable Kinetic Inductance in Proximitized Nanowires

Splitthoff, Lukas J.; Bargerbos, Arno; Grünhaupt, Lukas; Pita-Vidal, Marta; Wesdorp, Jaap J.; Liu, Yu; Kou, Angela; Andersen, Christian Kraglund; Heck, Bernard van

doi:10.1103/physrevapplied.18.024074

Cited by 15 publications

(17 citation statements)

References 62 publications

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“…The resulting phonons of energy E ≤ 2 trap can no longer excite quasiparticles in the qubit structures, for which the superconducting gaps of the islands, Nb-Ti-N ≥ 1500 µeV, and of the nanowires nw = 270 µeV are larger than that of the traps trap = 180 µeV (see Refs. [45][46][47]; see also the Supplemental Material [32]).…”

Section: Phonon Injection and Propagationmentioning

confidence: 99%

Mitigation of Quasiparticle Loss in Superconducting Qubits by Phonon Scattering

et al. 2023

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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 of high-energy phonons in the substrate. These phonons can break Cooper pairs in the superconductor and, thus, create quasiparticles over large areas, consequently reducing qubit coherence across the quantum device in a correlated fashion. A potential mitigation technique is to place large volumes of normal or superconducting metal on the device, capable of reducing the phonon energy to below the superconducting gap of the qubits. To investigate the effectiveness of this method, we fabricate a quantum device with four nominally identical nanowire-based transmon qubits. On the device, half of the niobium-titanium-nitride ground plane is replaced with aluminum (Al), which has a significantly lower superconducting gap. We deterministically inject high-energy phonons into the substrate by voltage biasing a galvanically isolated Josephson junction. In the presence of the small-gap material, we find a factor of 2-5 less degradation in the injection-dependent qubit lifetimes and observe that the undesired excited qubit state population is mitigated by a similar factor. We furthermore turn the Al normal with a magnetic field, finding no change in the phonon protection. This suggests that the efficacy of the protection in our device is not limited by the size of the superconducting gap in the Al ground plane. Our results provide a promising foundation for protecting superconducting-qubit processors against correlated errors from ionizing radiation.

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Section: Phonon Injection and Propagationmentioning

confidence: 99%

Mitigation of Quasiparticle Loss in Superconducting Qubits by Phonon Scattering

et al. 2023

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“…Using the value of L 0 for TR2 and L K calculated by the kinetic inductance fraction, we find that at the lowest gate voltage measured p J = 44.72%, implying significant participation of the junction in the circuit. Previous studies based on Al-InAs nanowires have been restricted by either a limited tunability range or discrete switching of the coupler frequency [41,73]. The wide range and continuous tunability of this 2DEGbased device are advantageous for tunable coupling schemes.…”

Section: Gate Voltage Tunabilitymentioning

confidence: 99%

Superconducting resonators with voltage-controlled frequency and nonlinearity

Strickland¹,

Elfeky²,

Yuan³

et al. 2022

Preprint

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Voltage-tunable superconductor-semiconductor devices offer a unique platform to realize dynamic tunability in superconducting quantum circuits. By galvanically connecting a gated InAs-Al Josephson junction to a coplanar waveguide resonator, we demonstrate the use of a wide-range gate-tunable superconducting element. We show that the resonant frequency is controlled via a gate-tunable Josephson inductance and that the non-linearity of the voltage-controlled InAs-Al junction is nondissipative as is the case with conventional Al-AlOx junctions. As the gate voltage is decreased, the inductive participation of the junction increases up to 44%, resulting in the resonant frequency being tuned by over 2 GHz. Utilizing the wide tunability of the device, we demonstrate that two resonant modes can be adjusted such that they strongly hybridize, exhibiting an avoided level crossing with a coupling strength of 51 MHz. Implementing such voltage-tunable resonators is the first step toward realizing wafer-scale continuous voltage control in superconducting circuits for qubit-qubit coupling, quantum-limited amplifiers, and quantum memory platforms.

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“…In experiments, a modest tunability of the superconducting gap 10 , 11 and the g - factor of Andreev bound states (ABSs) 12 , 13 have been reported. However, most experiments to date rely on tunneling measurements at the end of a nanowire, which only provide information on the local density of states.…”

Section: Introductionmentioning

confidence: 99%

Electrostatic control of the proximity effect in the bulk of semiconductor-superconductor hybrids

et al. 2023

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The proximity effect in semiconductor-superconductor nanowires is expected to generate an induced gap in the semiconductor. The magnitude of this induced gap, together with the semiconductor properties like spin-orbit coupling and g-factor, depends on the coupling between the materials. It is predicted that this coupling can be adjusted through the use of electric fields. We study this phenomenon in InSb/Al/Pt hybrids using nonlocal spectroscopy. We show that these hybrids can be tuned such that the semiconductor and superconductor are strongly coupled. In this case, the induced gap is similar to the superconducting gap in the Al/Pt shell and closes only at high magnetic fields. In contrast, the coupling can be suppressed which leads to a strong reduction of the induced gap and critical magnetic field. At the crossover between the strong-coupling and weak-coupling regimes, we observe the closing and reopening of the induced gap in the bulk of a nanowire. Contrary to expectations, it is not accompanied by the formation of zero-bias peaks in the local conductance spectra. As a result, this cannot be attributed conclusively to the anticipated topological phase transition and we discuss possible alternative explanations.

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Gate-Tunable Kinetic Inductance in Proximitized Nanowires

Cited by 15 publications

References 62 publications

Mitigation of Quasiparticle Loss in Superconducting Qubits by Phonon Scattering

Mitigation of Quasiparticle Loss in Superconducting Qubits by Phonon Scattering

Superconducting resonators with voltage-controlled frequency and nonlinearity

Electrostatic control of the proximity effect in the bulk of semiconductor-superconductor hybrids

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