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

TL;DR

This paper reports the first direct observation of the 4π-periodic Josephson effect in InAs nanowires, providing evidence for Majorana zero modes and advancing topological quantum computation.

Contribution

It demonstrates charge parity conserving measurements of the Josephson effect in InAs nanowires, confirming the topological phase transition and the presence of Majorana modes.

Findings

Observation of 4π-periodic Josephson effect above 200 mT

Consistent with topological phase transition

Supports Majorana zero modes in nanowires

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 leads to 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 InAs nanowires with epitaxial aluminium shells. For the first time, we observe the $4\pi$-periodic Josephson effect above a magnetic field of $\approx 200\,$mT, consistent with the estimated and measured topological phase transition of similar devices.