We report an experimental study of the scaling of zero-bias conductance peaks compatible with Majorana zero modes as a function of magnetic field, tunnel coupling, and temperature in onedimensional structures fabricated from an epitaxial semiconductor-superconductor heterostructure. Results are consistent with theory, including a peak conductance that is proportional to tunnel coupling, saturates at 2e 2 /h, decreases as expected with field-dependent gap, and collapses onto a simple scaling function in the dimensionless ratio of temperature and tunnel coupling.Recent years have seen rapid progress in the study of Majorana zero modes (MZMs) in condensed matter. Following initial reports of zero-bias peaks (ZBPs) in conductance of nanowire-superconductor hybrids appearing at moderate magnetic fields [1], improvements in materials [2-4] resulted in harder induced gaps and the emergence of zero-bias peaks from coalescing Andreev bound states (ABSs) [5,6], as well as the observation of exponential suppression of Coulomb peak oscillations with nanowire length [7]. Recently, indications of MZMs were also identified in wires lithographically patterned on hybrid two-dimensional heterostructures [8,9]. In many respects, experimentally observed ZBPs are consistent with theoretical expectations for MZMs, but important questions remain, particularly concerning theoretical models that show ZBPs arising from nontopological ABSs in localized states at the wire ends [10,11]. Furthermore, the fact that observed zero-bias peaks [1,5,6,12] were considerably smaller than the theoretically expected value of 2e 2 /h [13-18] has raised concern. Speculations about the origin of this discrepancy included effects of dissipation [19] as well as nontopological ZBPs induced by disorder [20][21][22] or a spin-orbit-induced precursor [10].In this Letter, we investigate ZBPs in lithographically defined wires as a function of temperature, tunnel coupling to a metallic lead (parametrized by the normal state conductance G N ), and magnetic field. For weak coupling to the lead (G N e 2 /h), a small ZBP with strong temperature dependence is observed over an extended range of magnetic fields. For strong coupling (G N ∼ e 2 /h), the dependence of the ZBP on G N and temperature weakens, with a low-temperature saturation at ∼ 2e 2 /h. Experimental results are well described by a theoretical model of resonant transport through a zero-energy state that includes both broadening due to coupling to a normal lead and temperature.Fitting ZBP heights as a function of temperature, T , and G N yields values for the energy broadening, Γ, which we find obey the linear relationship Γ ∝ G N . The fit results for Γ are found to be in excellent agreement with a scaling function that depends only on the dimensionless ratio Γ/k B T . The observed magnetic field dependence of the ZBP is quantitatively consistent with a picture in which field reduces the induced superconducting gap, ∆ * , which in turn reduces the ZBP height through the dependence of Γ on ∆ * .Overall, the...

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The coherent tunnelling of Cooper pairs across Josephson junctions (JJs) generates a nonlinear inductance that is used extensively in quantum information processors based on superconducting circuits, from setting qubit transition frequencies and interqubit coupling strengths to the gain of parametric amplifiers for quantum-limited readout. The inductance is either set by tailoring the metal oxide dimensions of single JJs, or magnetically tuned by parallelizing multiple JJs in superconducting quantum interference devices with local current-biased flux lines. JJs based on superconductor-semiconductor hybrids represent a tantalizing all-electric alternative. The gatemon is a recently developed transmon variant that employs locally gated nanowire superconductor-semiconductor JJs for qubit control. Here we go beyond proof-of-concept and demonstrate that semiconducting channels etched from a wafer-scale two-dimensional electron gas (2DEG) are a suitable platform for building a scalable gatemon-based quantum computer. We show that 2DEG gatemons meet the requirements by performing voltage-controlled single qubit rotations and two-qubit swap operations. We measure qubit coherence times up to ~2 μs, limited by dielectric loss in the 2DEG substrate.

A differential capacitance‐voltage method for determining doping profiles in depth in epitaxial semiconductor films is described. Experimental profiles, in which the doping level generally is not flat but decreases with film thickness, are shown for several film growth conditions. A possible explanation for the observed distribution is discussed.