Flip-Chip-Based Microwave Spectroscopy of Andreev Bound States in a Planar Josephson Junction

Hinderling, M.; Sabonis, Deividas; Paredes, Stephan; Haxell, D. Z.; Coraiola, M.; Kate, S. C. ten; Cheah, Erik; Schott, Rüdiger; Wegscheider, Werner; Nichele, Fabrizio

doi:10.1103/physrevapplied.19.054026

Cited by 8 publications

(2 citation statements)

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“…The discrepancy might be due to the presence of many transverse modes, which future studies could investigate by varying the junction dimensions or by isolating individual modes using gate voltages. 64 Type B shifts were consistent with a 0−π transition, where orbital effects in the superconducting leads played a critical role. This suggests that the geometry of the superconducting leads, and their impact on orbital effects, is a key ingredient for realizing π-junctions for superconducting electronics 65 , 66 or in interpreting signatures of topological superconductivity.…”

Section: Discussionmentioning

confidence: 67%

“…Highly transmissive bound states were shown to make a significant contribution to the phase shift, which was much larger than expected for a single ballistic channel. The discrepancy might be due to the presence of many transverse modes, which future studies could investigate by varying the junction dimensions or by isolating individual modes using gate voltages . Type B shifts were consistent with a 0−π transition, where orbital effects in the superconducting leads played a critical role.…”

Section: Discussionmentioning

confidence: 92%

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Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions

Haxell,

Coraiola,

Sabonis

et al. 2023

ACS Nano

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We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field and report on phase shifts in the current–phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to φ 0 = 0.5π, which are consistent with a Zeeman field coupling to highly transmissive Andreev bound states via Rashba spin–orbit interaction. A distinct phase shift emerges at larger fields, concomitant with a switching current minimum and the closing and reopening of the superconducting gap. These signatures of an induced phase transition, which might resemble a topological transition, scale with the superconducting lead size, demonstrating the crucial role of orbital effects. Our results elucidate the interplay of Zeeman, spin–orbit, and orbital effects in InAs/Al JJs, giving improved understanding of phase transitions in hybrid JJs and their applications in quantum computing and superconducting electronics.

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Section: Discussionmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 92%

Zeeman- and Orbital-Driven Phase Shifts in Planar Josephson Junctions

Haxell,

Coraiola,

Sabonis

et al. 2023

ACS Nano

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A gate tunable transmon qubit in planar Ge

Sagi,

Crippa,

Valentini

et al. 2024

Nat Commun

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Gate-tunable transmons (gatemons) employing semiconductor Josephson junctions have recently emerged as building blocks for hybrid quantum circuits. In this study, we present a gatemon fabricated in planar Germanium. We induce superconductivity in a two-dimensional hole gas by evaporating aluminum atop a thin spacer, which separates the superconductor from the Ge quantum well. The Josephson junction is then integrated into an Xmon circuit and capacitively coupled to a transmission line resonator. We showcase the qubit tunability in a broad frequency range with resonator and two-tone spectroscopy. Time-domain characterizations reveal energy relaxation and coherence times up to 75 ns. Our results, combined with the recent advances in the spin qubit field, pave the way towards novel hybrid and protected qubits in a group IV, CMOS-compatible material.

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