Voltage-controlled synthesis of higher harmonics in hybrid Josephson junction circuits

TL;DR

This study demonstrates voltage-controlled tuning of harmonic content in hybrid Josephson junction circuits, revealing how gate voltages can modulate the current-phase relation from sinusoidal to nonsinusoidal forms.

Contribution

It introduces a model explaining harmonic tuning in series hybrid JJs using gate voltages, advancing control over their quantum properties.

Findings

Harmonic content can be tuned from sinusoidal to nonsinusoidal.

The behavior of two hybrid JJs in series mimics a single-mode JJ.

Experimental results align with the sinusoidal series junction model.

Abstract

We report measurements of the current-phase relation of two voltage-controlled semiconductor-superconductor hybrid Josephson junctions (JJs) in series. The two hybrid junctions behave similar to a single-mode JJ with effective transparency determined by the ratio of Josephson coupling strengths of the two junctions. Gate-voltage control of Josephson coupling (measured from switching currents) allows tuning of the harmonic content from sinusoidal, for asymmetric tuning, to highly nonsinusoidal, for symmetric tuning. The experimentally observed tunable harmonic content agrees with a model based on two conventional (sinusoidal) JJs in series.