Observation of the 4\u03c0-periodic Josephson effect in indium arsenide nanowires

Dominique Laroche,Attila Geresdi,Peter Krogstrup,Alex Proutski,Chaitanya Murthy,David J Van Woerkom,Leo P Kouwenhoven,Daniël Bouman,Jesper Nygård,Chetan Nayak,Ruben J J Van Gulik,Dmitry I Pikulin

doi:10.1038/s41467-018-08161-2

Abstract

Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime. Thus far, experimental studies of MZMs chiefly relied on single electron tunneling measurements, which lead to the decoherence of the quantum information stored in the MZM. As a next step towards topological quantum computation, charge parity conserving experiments based on the Josephson effect are required, which can also help exclude suggested non-topological origins of the zero bias conductance anomaly. Here we report the direct measurement of the Josephson radiation frequency in indium arsenide nanowires with epitaxial aluminium shells. We observe the 4π-periodic Josephson effect above a magnetic field of ≈200 mT, consistent with the estimated and measured topological phase transition of similar devices.

Highlights

Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime
Φ0 is the superconducting flux quantum. This relation, describing the conventional, 2π-periodic Josephson effect, can be understood as the tunneling of Cooper pairs with a net charge e* = 2e coupled to photons of energy hf[2]
As a frequency-sensitive microwave detector, we utilized a superconducting tunnel junction with a quasiparticle gap of ΔDET, wherein the photon-assisted electron tunneling (PAT) current contributed to the DC current above a voltage bias threshold eVDET > 2ΔDET - hf[22,28] (Fig. 1c)

Summary

Introduction

Quantum computation by non-Abelian Majorana zero modes (MZMs) offers an approach to achieve fault tolerance by encoding quantum information in the non-local charge parity states of semiconductor nanowire networks in the topological superconductor regime. This relation, describing the conventional, 2π-periodic Josephson effect, can be understood as the tunneling of Cooper pairs with a net charge e* = 2e coupled to photons of energy hf[2]. This coupling, referred to as the AC. Josephson effect, has first been measured in superconducting tunnel junctions[3] and has been shown to persist in metallic weak links[4], carbon nanotubes[5] and semiconductor channels[6,7], as well as in high critical temperature superconductors[8]

Methods

Results

Conclusion