Microwave Signatures of Topological Superconductivity in Planar Josephson Junctions

TL;DR

This paper theoretically investigates microwave signatures in planar Josephson junctions to identify topological superconductivity, focusing on distinguishing topological signals from trivial effects for quantum computing applications.

Contribution

It demonstrates that microwave resonance frequency shifts and absorption features can reveal topological superconductivity even with many trivial states present.

Findings

Topological gap closing and reopening produce detectable microwave signatures.

Microwave resonance frequency shifts indicate topological phase transitions.

Half-slope features in microwave absorption spectra serve as topological indicators.

Abstract

Planar Josephson junctions provide a platform to host topological superconductivity which, through manipulating Majorana bound states (MBS), could enable fault-tolerant quantum computing. However, what constitutes experimental signatures of topological superconductivity and how MBS can be detected remains strongly debated. In addition to spurious effects that mimic MBS, there is a challenge to discern the inherent topological signals in realistic systems with many topologically-trivial Andreev bound states, determining the transport properties of Josephson junctions. Guided by the advances in microwave spectroscopy, we theoretically study Al/InAs-based planar Josephson junction embedded into a radio-frequency superconducting quantum interference device to identify microwave signatures of topological superconductivity. Remarkably, by exploring the closing and reopening of a topological gap, we show that even in a wide planar Josephson junction with many Andreev bound states, such a topological signature is distinguishable in the resonance frequency shift of a microwave drive and the ``half-slope'' feature of the microwave absorption spectrum. Our findings provide an important step towards experimental detection of non-Abelian statistics and implementing scalable topological quantum computing.