AC Josephson effect in finite-length nanowire junctions with Majorana modes

TL;DR

This paper demonstrates that the anomalous 4π-periodic Josephson effect in topological nanowire junctions with Majorana bound states can be observed in transient ac regimes, protected by the quantum Zeno effect, offering a new detection method.

Contribution

It reveals that the 4π-periodic Josephson effect persists in transient regimes despite finite-length wire limitations, and shows how the quantum Zeno effect stabilizes this anomaly for detection.

Findings

Transient ac Josephson effect reveals Majorana modes.

Quantum Zeno effect stabilizes parity, protecting the anomaly.

Potential for experimental detection of Majorana bound states.

Abstract

It has been predicted that superconducting junctions made with topological nanowires hosting Majorana bound states (MBS) exhibit an anomalous 4\pi-periodic Josephson effect. Finding an experimental setup with these unconventional properties poses, however, a serious challenge: for finite-length wires, the equilibrium supercurrents are always 2\pi-periodic as anticrossings of states with the same fermionic parity are possible. We show, however, that the anomaly survives in the transient regime of the ac Josephson effect. Transients are moreover protected against decay by quasiparticle poisoning as a consequence of the quantum Zeno effect, which fixes the parity of Majorana qubits. The resulting long-lived ac Josephson transients may be effectively used to detect MBS.