Non-Majorana states yield nearly quantized conductance in proximatized nanowires

Yu, Peng; Chen, Jun; Gomanko, Maksim; Badawy, Ghada; Bakkers, Erik P. A. M.; Zuo, Kun; Mourik, Vincent; Frolov, Sergey

doi:10.1038/s41567-020-01107-w

Cited by 140 publications

(105 citation statements)

References 52 publications

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“…Theoretical studies recently pointed out that partially or fully overlapping MBS can cause quantised ZBPs, indistinguishable from those resulting from isolated MBS 55 , 57 , 58 . Hence, the quantised ZBP conductance is a critical but not sufficient hallmark of MBS 54 , 58 .…”

Section: Resultsmentioning

confidence: 99%

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Shadow-wall lithography of ballistic superconductor–semiconductor quantum devices

et al. 2021

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The realization of hybrid superconductor–semiconductor quantum devices, in particular a topological qubit, calls for advanced techniques to readily and reproducibly engineer induced superconductivity in semiconductor nanowires. Here, we introduce an on-chip fabrication paradigm based on shadow walls that offers substantial advances in device quality and reproducibility. It allows for the implementation of hybrid quantum devices and ultimately topological qubits while eliminating fabrication steps such as lithography and etching. This is critical to preserve the integrity and homogeneity of the fragile hybrid interfaces. The approach simplifies the reproducible fabrication of devices with a hard induced superconducting gap and ballistic normal-/superconductor junctions. Large gate-tunable supercurrents and high-order multiple Andreev reflections manifest the exceptional coherence of the resulting nanowire Josephson junctions. Our approach enables the realization of 3-terminal devices, where zero-bias conductance peaks emerge in a magnetic field concurrently at both boundaries of the one-dimensional hybrids.

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Section: Resultsmentioning

confidence: 99%

“…So far, no experiment has revealed the emergence of ZBPs concurrently at both boundaries of a long hybrid nanowire. Recent experimental studies reported correlations between bound states at both ends of short (up to 400 nm long) hybrid nanowire devices 53 , 54 . ZBPs often originate from trivial Andreev bound states (ABS).…”

Section: Resultsmentioning

confidence: 99%

Shadow-wall lithography of ballistic superconductor–semiconductor quantum devices

et al. 2021

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“…Science published an experiment led by researchers at Pennsylvania State University in University Park contradicting the 2017 report 4 . My group reproduced patterns from the 2018 Nature study, but demonstrated that they need not originate from Majorana 5 . We did a cross-check on both ends of the same nanowire, but found a current peak on only one end.…”

Section: Challenging Sciencementioning

confidence: 73%

Quantum computing’s reproducibility crisis: Majorana fermions

Frolov¹

2021

Nature

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Ashadow has fallen over the race to detect a new type of quantum particle, the Majorana fermion, that could power quantum computers. As someone who works in this area, I've become concerned that, after a series of false starts, a significant fraction of the Majorana field is fooling itself. Several key experiments claiming to have detected Majorana particles, initially considered as breakthroughs, have not been confirmed. One recent case ended in a high-profile retraction from Nature (see Nature 591, 354-355; 2021), which I initiated with my colleague Vincent Mourik, a physicist at the University of New South Wales in Sydney, Australia. We raised concerns after obtaining additional data from the original experiments that were not included with the published paper.Much is at stake. Majorana particles are in theory their own antiparticles, and were predicted in 1937 by Italian physicist Ettore Majorana. Computer giant Microsoft hopes to use Majorana particles to build a reliable quantum computer: the particles should make for exceptionally stable quantum bits. The scientific excitement around them is on a par with gravitational waves and the Higgs boson.Experimentally, researchers are at loggerheads over whether Majoranas have been detected at all, let alone whether they're an asset for quantum computing. As scepticism of the claims creeps beyond the cognoscenti, the field is at risk of getting a bad reputation, despite its untapped promise.

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“…Although finite temperature effects can flatten the isoconductance plateaus of Fig. 2 64 , quantized conductance values near may still be obtained in a realistic experimental situation when the QD-TSC coupling is dominant over both the temperature and the overlap between the MBSs 41 , 69 . Previously some of us have studied the interplay between the thermal broadening and the overlap strength of the MBSs via NRG analysis 69 .…”

Section: Resultsmentioning

confidence: 98%

Topological isoconductance signatures in Majorana nanowires

Ricco

Sanches

Marques

et al. 2021

Sci Rep

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We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. It is demonstrated that if highly nonlocal and nonoverlapping MBSs are formed in the system, the zero-bias Andreev conductance through the dot exhibits characteristic isoconductance profiles with the shape depending on the spin asymmetry of the coupling between the dot and the topological superconductor. Otherwise, for overlapping MBSs with less degree of nonlocality, the conductance is insensitive to the spin polarization and the isoconductance signatures disappear. This allows to propose an alternative experimental protocol for probing the nonlocality of the MBSs in Majorana nanowires.

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Non-Majorana states yield nearly quantized conductance in proximatized nanowires

Cited by 140 publications

References 52 publications

Shadow-wall lithography of ballistic superconductor–semiconductor quantum devices

Shadow-wall lithography of ballistic superconductor–semiconductor quantum devices

Quantum computing’s reproducibility crisis: Majorana fermions

Topological isoconductance signatures in Majorana nanowires

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