Gate- and flux-tunable sin(2$\phi$) Josephson element with proximitized Ge-based junctions

Abstract

Hybrid superconductor-semiconductor Josephson field-effect transistors (JoFETs) function as Josephson junctions with a gate-tunable critical current. Additionally, they can feature a non-sinusoidal current-phase relation (CPR) containing multiple harmonics of the superconducting phase difference, a so-far underutilized property. In this work, we exploit this multi-harmonicity to create a Josephson circuit element with an almost perfectly $\pi$-periodic CPR, indicative of a largely dominant charge-4e supercurrent transport. Such a Josephson element was recently proposed as the basic building block of a protected superconducting qubit. Here, it is realized using a superconducting quantum interference device (SQUID) with low-inductance aluminum arms and two nominally identical JoFETs. The latter are fabricated from a SiGe/Ge/SiGe quantum-well heterostructure embedding a high-mobility two-dimensional hole gas. By carefully adjusting the JoFET gate voltages and finely tuning the magnetic flux through the SQUID close to half a flux quantum, we achieve a regime where the $\sin (2\phi )$ component accounts for more than \SI{95}{\percent} of the total supercurrent. This result demonstrates a new promising route for the realization of superconducting qubits with enhanced coherence properties.

References in corpus (37)

• Charge insensitive qubit design derived from the Cooper pair box
• Fluxonium: single Cooper pair circuit free of charge offsets
• A Josephson junction supercurrent diode
• The Future of Quantum Computing with Superconducting Qubits
• Realization of microwave quantum circuits using hybrid superconducting-semiconducting nanowire Josephson elements
• Superconducting Nanocircuits for Topologically Protected Qubits
• Pairing of Cooper Pairs in a Fully Frustrated Josephson Junction Chain
• Experimental realization of an intrinsically error-protected superconducting qubit
• Measurement of the current-phase relation of superconducting atomic contacts
• Possible realization of an ideal quantum computer in Josephson junction array
• Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry
• Non-sinusoidal current-phase relationship in Josephson junctions from the 3D topological insulator HgTe
• Moving beyond the transmon: Noise-protected superconducting quantum circuits
• A Parity-Protected Superconductor-Semiconductor Qubit
• Current-phase relations of few-mode InAs nanowire Josephson junctions
• Relating Andreev Bound States and Supercurrents in Hybrid Josephson Junctions
• Superconducting circuit protected by two-Cooper-pair tunneling
• Current-phase relation of ballistic graphene Josephson junctions
• Protected Josephson Rhombi Chains
• Parity-conserving Cooper-pair transport and ideal superconducting diode in planar Germanium
• Bifluxon: Fluxon-Parity-Protected Superconducting Qubit
• Second-harmonic current-phase relation in Josephson junctions with ferromagnetic barriers
• A Tunable Monolithic SQUID in Twisted Bilayer Graphene
• A gate tunable transmon qubit in planar Ge
• Charge-4e supercurrent in a two-dimensional InAs-Al superconductor-semiconductor heterostructure
• Protected qubit based on a superconducting current mirror
• Magnifying quantum phase fluctuations with Cooper-pair pairing
• Current-phase relation of a WTe2 Josephson junction
• Entangling transmons with low-frequency protected superconducting qubits
• Half-Integer Shapiro Steps in a Short Ballistic InAs Nanowire Josephson Junction
• Multi-mode architectures for noise-resilient superconducting qubits
• Limitations of the current-phase relation measurements by an asymmetric dc-SQUID
• Direct measurement of a $\sin (2\phi )$ current phase relation in a graphene superconducting quantum interference device
• Direct microwave spectroscopy of Andreev bound states in planar Ge Josephson junctions
• Gatemon qubit on a germanium quantum-well heterostructure
• From nonreciprocal to charge-4e supercurrents in Ge-based Josephson devices with tunable harmonic content
• Voltage-controlled synthesis of higher harmonics in hybrid Josephson junction circuits